Canned motor and vacuum pump

ABSTRACT

Provided is a canned motor to be coupled to a vacuum pump and used as a rotary driving source for the vacuum pump. The canned motor includes: a stator core; a rotor provided on an inner side of the stator core; and a non-conductive can provided between the stator core and the rotor. The non-conductive can is configured to separate the stator core and the rotor from each other. The non-conductive can is made of resin, ceramic, or composite material thereof. The non-conductive can is bonded to the stator core with an adhesive.

CROSS-REFERENCE TO RELATED APPLICATIONS

This document is a Divisional Application of U.S. application Ser. No.14/858,873, filed on Sep. 18, 2015, which is a Divisional Application ofSer. No. 13/853,005 filed Mar. 28, 2013, which claims priority toJapanese Patent Application Nos. 2013-012284 filed on Jan. 25, 2013,2012-179328 filed on Aug. 13, 2012, 2012-179332 filed on Aug. 13, 2012,2012-179335 filed on Aug. 13, 2012 and 2012-077487 filed on Mar. 29,2012, the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a canned motor.

BACKGROUND ART

A vacuum pump including a motor, which is described in, for example,JP2005-184958A, is conventionally known. The above-mentioned vacuum pumpis widely used to exhaust a process gas in a vacuum chamber duringsemiconductor manufacturing steps.

In the motor for the vacuum pump described above, a rotor chamber forseparating a motor stator and a motor rotor is formed so as to seal thevacuum pump. The rotor chamber is a space which is hermetically sealedwith respect to the motor stator by a partition, that is, a can fixed tothe vacuum pump side. The motor having a structure in which the motorstator and the motor rotor are separated from each other by the can asdescribed above is referred to as a canned motor. The canned motor isgenerally provided to an end portion of a pump rotor of the vacuum pumpso as to be directly coupled to the pump rotor.

For the canned motor described above, a can made of non-magnetic metalsuch as stainless steel with a small thickness has been conventionallyused. When the can made of non-magnetic metal is used, however, an eddycurrent is generated in a surface under the effect of a magnetic fluxfrom the motor stator. By a loss generated by the generation of the eddycurrent, motor efficiency is lowered. On the other hand, a can membermade of resin is also used. However, a thickness size of the partitionis set larger as compared with that of the can member made of metal soas to maintain a mechanical strength of the partition. For example, inthe case of a pump for delivering a chemical solution, in general, apressure fluctuation is scarcely generated as a result of a reducedpressure inside the motor stator. Moreover, a pressure fluctuation in acompressing direction with respect to the can member, which is generatedon the atmosphere side around the motor, is also extremely small. On thecontrary, a pressure in a direction in which the can member expandsoutward is generally applied. In this case, the applied pressure issupported by the stator core located on the outer circumference of thecan member. Therefore, even the can member having a relatively smallthickness does not expand to burst. On the other hand, in the case ofthe canned motor for the vacuum pump, a large pressure in thecompressing direction directly acts on the can member by a difference inpressure between a pressure in a vacuum region in the rotor chamber andthe atmospheric pressure around the motor, which is generated during theoperation. In other words, the can member is subjected to a largetensile force acting toward the interior of the rotor chamber.Therefore, in the case of the canned motor for the vacuum pump, astrength of the can member is increased by increasing the thickness ofthe can member to prevent radially inward buckling distortion of the canmember by a compressing force.

For the canned motor including the can made of resin, when the thicknessof the can is set too small, the mechanical strength of the can islowered. As a result, there is a fear in that the can cannot resist tothe pressure fluctuation in the vacuum pump. Therefore, the reduction inthe thickness of the can is limited. The thickness of the can made ofresin is generally set based on a pressure vessel calculating methoddescribed in JIS B8267 and the like, and is about 1.5 to 2.0 mm.

SUMMARY OF INVENTION

According to one embodiment of the present invention, a canned motor tobe coupled to a vacuum pump and used as a rotary driving source for thevacuum pump is provided. The canned motor includes: a stator core; arotor provided on an inner side of the stator core; and a non-conductivecan provided between the stator core and the rotor. The non-conductivecan is configured to separate the stator core and the rotor from eachother in a state in which the non-conductive can is held in contact withthe stator core. The non-conductive can is made of resin, ceramic, orcomposite material thereof. The non-conductive can is bonded to thestator core with an adhesive.

According to one embodiment of the present invention, a canned motor tobe coupled to a vacuum pump and used as a rotary driving source for thevacuum pump is provided. The canned motor includes: a stator core; arotor provided on an inner side of the stator core; and a can made ofresin provided between the stator core and the rotor. The can isconfigured to separate the stator core and the rotor from each other.The can includes a barrel portion having a hollow shape and extending ina direction of a rotation center axis line of the rotor. At least one ofan outer-diameter side surface and an inner-diameter side surface of thebarrel portion is approximately horizontal with an inclination ofsmaller than 0.5 degrees with respect to the rotation center axis linewithin at least a part of a range facing the stator core in thedirection of the rotation center axis line.

According to one embodiment of the present invention, there is provideda canned motor to be used to rotationally drive a vacuum pump, thecanned motor including a stator and a rotor separated from each other bya cylindrical resin partition covering an inter circumferential portionof the stator, in which an outer circumferential portion of thecylindrical resin partition forms a meshing portion to be brought intomeshing engagement with magnetic-pole tooth portions of the stator in aradial direction.

According to one embodiment of the present invention, a canned motor tobe coupled to a vacuum pump and used as a rotary driving source for thevacuum pump is provided. The canned motor includes: a stator core; arotor provided on an inner side of the stator core; and a can providedbetween the stator core and the rotor. The can is configured to separatethe stator core and the rotor from each other. The can includes: abarrel portion having a hollow shape and extending in a direction of arotation center axis line of the rotor; and an opening portion forforming an opening of the barrel portion on a first side directlycoupled to the vacuum pump in the direction of the rotation center axisline. The stator core and the rotor are separated from each other in ahermetically sealed manner by the can and an O-ring provided on an outersurface of the opening portion of the can along a circumferentialdirection.

BRIEF DESCRIPTION OF DRAWINGS

In the accompanying drawings:

FIG. 1 is an explanatory view illustrating a schematic configuration ofa vacuum pump according to Embodiment 1-A of the present invention;

FIG. 2 is an explanatory view illustrating a schematic configuration ofa canned motor according to Embodiment 1-A;

FIG. 3A is an explanatory view illustrating a configuration of a can ofa canned motor according to Embodiment 1-B;

FIG. 3B is an explanatory view illustrating the configuration of the canof the canned motor according to Embodiment 1-B;

FIG. 4 is a partial sectional view illustrating a configuration of a canof a canned motor according to Embodiment 1-C;

FIG. 5 is a sectional view illustrating a configuration in which a canand a stator core are bonded according to Embodiment 1-D;

FIG. 6 is a sectional view illustrating a configuration in which a canand a stator core are bonded according to Embodiment 1-E;

FIG. 7 is an explanatory view illustrating a schematic configuration ofa canned motor according to Embodiment 2-A;

FIG. 8 is an explanatory view illustrating a method of manufacturing thecan;

FIG. 9 is a perspective view illustrating the details of a partitionaccording to Embodiment 3-A;

FIG. 10 is a perspective view illustrating another example of theconfiguration of the partition;

FIG. 11 is a sectional view of the motor taken along a radial direction;

FIG. 12 is a partially enlarged view of FIG. 11;

FIG. 13 is a partial sectional view illustrating the details of thepartition;

FIG. 14 is a partial sectional view illustrating another example of ameshing portion of the partition;

FIG. 15 is a partial sectional view illustrating a further example ofthe meshing portion of the partition;

FIG. 16 is a partial sectional view illustrating a further example ofthe meshing portion of the partition;

FIG. 17 is a partial sectional view illustrating a further example ofthe meshing portion of the partition;

FIG. 18 is an explanatory view illustrating a schematic configuration ofa canned motor according to Embodiment 4-A;

FIG. 19 is an explanatory view illustrating a schematic configuration ofa canned motor according to a comparative example;

FIG. 20 is an explanatory view illustrating a configuration of a can ofa canned motor according to Embodiment 4-B; and

FIG. 21 is a diagram illustrating the can as viewed from anopening-portion side.

DESCRIPTION OF EMBODIMENTS 1. First Embodiment Group

According to one embodiment of the present invention, a canned motor tobe coupled to a vacuum pump and used as a rotary driving source for thevacuum pump is provided. The canned motor includes: a stator core; arotor provided on an inner side of the stator core; and a non-conductivecan provided between the stator core and the rotor. The non-conductivecan is configured to separate the stator core and the rotor from eachother in a state in which the non-conductive can is held in contact withthe stator core. The non-conductive can is made of resin, ceramic, orcomposite material thereof. The non-conductive can is bonded to thestator core with an adhesive.

With the canned motor described above, the non-conductive can and thestator core are held in contact with each other, and are further bondedwith an adhesive. Therefore, in this state, the non-conductive can andthe stator core are integrated with each other. Thus, a mechanicalstrength of a part of the non-conductive can, which is located at theposition corresponding to the stator core, can be reinforced by thestator core. Therefore, a thickness of the part of the non-conductivecan made of resin at the position corresponding to the stator core canbe correspondingly reduced. As a result, motor characteristics can beimproved.

According to one embodiment of the present invention, a canned motor tobe coupled to a vacuum pump and used as a rotary driving source for thevacuum pump is provided. The canned motor includes: a stator core; arotor provided on an inner side of the stator core; and a non-conductivecan provided between the stator core and the rotor. The non-conductivecan is configured to separate the stator core and the rotor from eachother in a state in which the non-conductive can is held in contact withthe stator core. The non-conductive can is made of resin, ceramic, orcomposite material thereof. The non-conductive can is bonded to thestator core with an adhesive through an underlayer formed on an outersurface of the non-conductive can. The underlayer is formed of anon-conductive material having a higher affinity for the adhesive thanthe non-conductive can.

With the canned motor described above, a bonding strength between thestator core and the non-conductive can is improved. Therefore, themechanical strength of the non-conductive can can be further reinforcedby the stator core. As a result, the thickness of the non-conductive canmade of resin can be further reduced.

According to one embodiment of the present invention, the canned motormay further include an annular reinforcing member provided on an outerside of the stator core in a direction of a rotation center axis line ofthe rotor. The annular reinforcing member is held in contact with anouter surface of the non-conductive can in a circumferential direction.In the embodiment described above, the mechanical strength of thenon-conductive can can be reinforced by the annular reinforcing membereven in the region on the outer side of the stator core. Therefore, thethickness of the non-conductive can made of resin in the region on theouter side of the stator core can be correspondingly reduced.

According to one embodiment of the present invention, the non-conductivecan may be bonded to the annular reinforcing member with an adhesive. Inthe embodiment described above, the non-conductive can and the annularreinforcing member are formed integrally, and hence the mechanicalstrength of the non-conductive can can be further reinforced in theregion on the outer side of the stator core. Therefore, the thickness ofthe non-conductive can made of resin in the region on the outer side ofthe stator core can be correspondingly reduced.

According to one embodiment of the present invention, the non-conductivecan may be bonded to the annular reinforcing member with an adhesivethrough an underlayer formed on the outer surface of the non-conductivecan. The underlayer may be formed of non-conductive material having ahigher affinity for the adhesive than the annular reinforcing member. Inthe embodiment described above, the bonding strength between the annularreinforcing member and the non-conductive can is improved. Therefore,the annular reinforcing member can further reinforce the mechanicalstrength of the non-conductive can. As a result, the thickness of thenon-conductive can made of resin can be further reduced.

According to one embodiment of the present invention, a linear expansioncoefficient of the annular reinforcing member may be equal to or smallerthan a linear expansion coefficient of the stator core. In theembodiment described above, a stress acting on the non-conductive canfrom the annular reinforcing member can be reduced when compression heatis generated by driving the vacuum pump to thermally expand the annularreinforcing member. Therefore, the mechanical strength required for thenon-conductive can can be reduced. As a result, the thickness of thenon-conductive can can be reduced.

According to one embodiment of the present invention, a non-conductivemember to be engaged with a plurality of teeth projecting toward acenter of the stator core may be provided in spaces betweeninner-circumferential side end portions of the plurality of teeth in thestator core. In the embodiment described above, a bonding area with theadhesive becomes larger. Therefore, the bonding strength between thestator core and the non-conductive can can be enhanced. Therefore, themechanical strength of the non-conductive can can be further reinforcedby the stator core. As a result, the thickness of the non-conductive canmade of resin can be further reduced.

According to one embodiment of the present invention, the canned motormay further include a stator frame formed so as to be longer than thestator core in a direction of a rotation center axis line of the rotor.The stator frame is configured to fix the stator core in a state inwhich the stator core is fitted into an internal space of the statorframe. The canned motor may further include a resin for filling anenclosed space formed in a region between the stator frame and thenon-conductive can. The region corresponds to a coil portion projectingfrom both ends of the stator core in the direction of the rotationcenter axis line toward an outer side of the stator core. In theembodiment described above, the mechanical strength of thenon-conductive can can be further reinforced by the resin filling theenclosed space. Therefore, the thickness of the non-conductive can madeof resin in the region between the stator frame and the non-conductivecan can be correspondingly reduced.

According to one embodiment of the present invention, a linear expansioncoefficient of the resin filling the enclosed space may be equal to orsmaller than a linear expansion coefficient of the stator core. In theembodiment described above, the stress acting on the non-conductive canfrom the resin filling the enclosed space through the annularreinforcing member can be reduced when the compression heat is generatedby driving the vacuum pump to thermally expand the filling resin.Therefore, the mechanical strength required for the non-conductive cancan be reduced. As a result, the thickness of the non-conductive can canbe reduced.

According to one embodiment of the present invention, the non-conductivecan may include: a barrel portion having a hollow shape and extending ina direction of a rotation center axis line of the rotor; a closingportion for closing an internal space of the barrel portion on a firstside in the direction of the rotation center axis line; and an openingportion for forming an opening of the barrel portion on a second sideopposite to the first side. The closing portion may include a portionhaving an inner diameter decreasing from the second side toward thefirst side. In the embodiment described above, a volume of thenon-conductive can is reduced. As a result, when the vacuum pump isdriven, the amount of movement of a gas between the interior of thenon-conductive can and the vacuum pump (pump chamber) is reduced.Specifically, the amount of gas passing through a bearing portionprovided between the interior of the non-conductive can and the pumpchamber is reduced. Therefore, a reduction of a lubricant, which isgenerated with the movement of the gas, can be suppressed. As a result,a burden of the maintenance and management of the vacuum pump can bereduced.

According to one embodiment of the present invention, the closingportion may have a dome shape of which a central portion expands fromthe second side toward the first side. In the embodiment describedabove, a mechanical strength of the closing portion can be improved.Moreover, as a result of the improvement of the mechanical strength, thethickness of the closing portion can be reduced. When the thickness ofthe closing portion is reduced, a difference in thickness between thebarrel portion and the closing portion is reduced. Therefore, themanufacture of the non-conductive can made of resin by injection moldingis facilitated.

According to one embodiment of the present invention, a rib may beformed on at least one of a surface of the closing portion on the firstside and a surface of the closing portion on the second side. In theembodiment described above, the mechanical strength of the closingportion can be improved. Moreover, as a result of the improvement of themechanical strength, the thickness of the closing portion can bereduced. Further, in the injection molding, a molded product is left ininner molds (male molds) when the molded product is demolded aftermolding. Therefore, when the rib is formed on the second-side surface ofthe closing portion, the molded product is easily locked to the innermolds. As a result, the manufacture of the non-conductive can made ofresin by the injection molding is facilitated.

According to one embodiment of the present invention, a vacuum pump isprovided. The vacuum pump may include the canned motor in any one of theembodiments described above.

According to one embodiment of the present invention, a canned motor tobe coupled to a vacuum pump and used as a rotary driving source for thevacuum pump is provided. The canned motor includes: a stator core; arotor provided on an inner side of the stator core; and a can providedbetween the stator core and the rotor. The can is configured to separatethe stator core and the rotor from each other in a state in which thecan is held in contact with the stator core. The can includes: a barrelportion having a hollow shape and extending in a direction of a rotationcenter axis line of the rotor; a closing portion for closing an internalspace of the barrel portion on a first side in the direction of therotation center axis line; and an opening portion for forming an openingof the barrel portion on a second side opposite to the first side. Theclosing portion includes a portion having an inner diameter decreasingfrom the second side toward the first side.

According to one embodiment of the present invention, the closingportion may have a dome shape of which a central portion expands fromthe second side toward the first side. According to one embodiment ofthe present invention, a rib may be formed on at least one of a surfaceof the closing portion on the first side and a surface of the closingportion on the second side. Any combination of the various embodimentsdescribed above is possible.

Further, according to one embodiment of the present invention, a cannedmotor to be coupled to a vacuum pump and used as a rotary driving sourcefor the vacuum pump is provided. The canned motor includes: a statorcore; a rotor provided on an inner side of the stator core; and anon-conductive can provided between the stator core and the rotor. Thenon-conductive can is configured to separate the stator core and therotor from each other in a state in which the non-conductive can is heldin contact with the stator core. The non-conductive can is made ofresin, ceramic, or composite material thereof. The non-conductive can isbonded to the stator core with an adhesive. Further, according to oneembodiment of the present invention, a canned motor to be coupled to avacuum pump and used as a rotary driving source for the vacuum pump isprovided. The canned motor includes: a stator core; a rotor provided onan inner side of the stator core; and a non-conductive can providedbetween the stator core and the rotor The non-conductive can isconfigured to separate the stator core and the rotor from each other ina state in which the non-conductive can is held in contact with thestator core. The non-conductive can is made of resin, ceramic, orcomposite material thereof. The non-conductive can is bonded to thestator core with an adhesive through an underlayer formed on an outersurface of the non-conductive can. The underlayer is formed of anon-conductive material having a higher affinity for the adhesive thanthe non-conductive can. Further, according to one embodiment of thepresent invention, a canned motor to be coupled to a vacuum pump andused as a rotary driving source for the vacuum pump is provided. Thecanned motor includes: a stator core; a rotor provided on an inner sideof the stator core; and a can provided between the stator core and therotor. The can is configured to separate the stator core and the rotorfrom each other in a state in which the can is held in contact with thestator core. The can includes: a barrel portion having a hollow shapeand extending in a direction of a rotation center axis line of therotor; a closing portion for closing an internal space of the barrelportion on a first side in the direction of the rotation center axisline; and an opening portion for forming an opening of the barrelportion on a second side opposite to the first side. The closing portionincludes a portion having an inner diameter decreasing from the secondside toward the first side. The application of the canned motoraccording to each of the embodiments described above is not limited tothe pump, and the canned motor can also be applied to various pumps. Forexample, the canned motor according to each of the embodiments describedabove can be applied to liquid pumps and an air blower which is one kindof gas pumps in the broad sense of the term. Any combination of thecanned motor according to each of these embodiments with the variousembodiments described above applicable to the vacuum pump is possible.In the following, a first embodiment group of the present invention isdescribed with the exemplification of more specific embodiments. In thefollowing, the vacuum pump is described as an example. However, theembodiments described below are not limited to the vacuum pump asdescribed above.

1-A. Embodiment 1-A

FIG. 1 illustrates a schematic cross section of a vacuum pump 1-20. FIG.1 illustrates the cross section including a rotation center axis line ARof the vacuum pump 1-20. As illustrated in FIG. 1, the vacuum pump 1-20includes a pair of rotors 1-30 (only one thereof is illustrated in FIG.1). In this embodiment, each of the rotors includes a first-stage rotor1-31, a second-stage rotor 1-32, a third-stage rotor 1-33, and a pumpmain shaft 1-34. In the vicinity of both end portions of each of therotors 1-30, each of the rotors 1-30 is supported by a bearing 1-51provided to a bearing member 1-50 and a bearing 1-61 provided to abearing member 1-60. The rotor 1-30 is housed inside a casing 1-40. Anintake port (not shown) is formed in an upper part of the casing 1-40,whereas an exhaust port (not shown) is formed in a lower part of thecasing 1-40.

The rotor 1-30 is driven by a motor 1-100 provided on one end side ofthe rotation center axis line AR of the vacuum pump 1-20. A pair oftiming gears 1-70 (only one timing gear is illustrated in FIG. 1)meshing with each other is fixed to a shaft end of the pair of rotors1-30 on one end side. The other shaft end of each of the rotors 1-30 iscoupled to the motor 1-100. In this embodiment, the motor 1-100 is abrushless DC motor. FIG. 1 illustrates a configuration of the motor1-100 in a simplified manner.

When the motor 1-100 is driven, the rotors 1-30 rotate in the directionsopposite to each other in a non-contact manner while keeping slightclearances between an inner surface of the casing 1-40 and the rotors1-30 and between the rotors 1-30. With the rotation of the pair ofrotors 1-30, a gas on the suction side is enclosed between the rotors1-30 and the casing 1-40, and is then transferred to the discharge side.The gas introduced from the intake port (not shown) is transferred undercompression by the rotors 1-30 having the three-stage rotors, and isexhausted from the exhaust port (not shown).

FIG. 2 illustrates a schematic configuration of the motor 1-100 whichrotationally drives the rotors 1-30. In the following description, aside of the motor 1-100 to be coupled to the vacuum pump 1-20 (morespecifically, the rotors 1-30) in the direction of the rotation centeraxis line AR is also referred to as a coupling side S2, whereas a sideopposite to the coupling side S2 is also referred to as an outer sideS1. As illustrated in FIG. 2, the motor 1-100 includes a stator 1-110, arotor 1-120, a can 1-130, a stator frame 1-140, and reinforcing members1-150 and 1-160.

The stator frame 1-140 includes a frame main body 1-141 and a side plate1-142. The frame main body 1-141 has a cylindrical shape in which aninternal space is formed along the rotation center axis line AR. Theframe main body 1-141 includes a projecting portion 1-146. Theprojecting portion 1-146 is a portion which projects inward from aninner surface of the frame main body 1-141 and is formed in an annularshape around the rotation center axis line AR in the vicinity of an endportion of the frame main body 1-141 on the coupling side S2. A lengthof projection of the projecting portion 1-146 is formed so as to beapproximately equal to a length of projection of an opening portion1-133 from a barrel portion 1-131 (the details thereof are describedbelow). The side plate 1-142 has a circular plate shape, and closes anopening of the frame main body 1-141 on the outer side S1. A concaveportion 1-145 is formed on an end surface of the frame main body 1-141on the outer side S1. An O-ring 1-153 is provided in the concave portion1-145. The O-ring 1-153 is compressed in the direction of the rotationcenter axis line AR between the frame main body 1-141 and the side plate1-142 so as to perform sealing between the interior of the stator frame1-140 and the exterior thereof. The side plate 1-142 is mounted to theframe main body 1-141 with bolts (not shown). The stator frame 1-140 canbe formed of, for example, iron or aluminum. The stator 1-110, the rotor1-120, and the can 1-130 are housed in the internal space of the statorframe 1-140.

The stator 1-110 has a configuration in which coils are mounted to astator core 1-111. At both ends of the stator 1-110 in the direction ofthe rotation center axis line AR, coil portions 1-112 and 1-113 projectoutward from the stator core 1-111. By fitting the stator core 1-111into the interior of the frame main body 1-141 of the stator frame1-140, the stator 1-110 is fixed to the stator frame 1-140 coaxiallywith the rotation center axis line AR. The stator core 1-111 can beformed by, for example, laminating silicon steel plates. The rotor 1-120is provided coaxially with the rotation center axis line AR inside ofthe stator 1-110, and is directly coupled to the pump main shaft 1-34 ofthe rotor 1-30 of the vacuum pump 1-20.

The can 1-130 is provided between the stator 1-110 and the rotor 1-120described above. The can 1-130 separates the stator 1-110 and the rotor1-120 away from each other. The can 1-130 includes the barrel portion1-131, a closing portion 1-132, and the opening portion 1-133. Thebarrel portion 1-131 has an approximately cylindrical shape, and isprovided coaxially with the rotation center axis line AR. The barrelportion 1-131 is formed so as to extend over the range in which thestator 1-110 is provided in the direction of the rotation center axisline AR.

The closing portion 1-132 is an end surface of the can 1-130 on theouter side S1, and closes an internal space of the barrel portion 1-131at an end portion of the barrel portion 1-131 on the outer side S1. Theopening portion 1-133 is an end portion of the can 1-130 on the couplingside S2, and forms an opening of the can 1-130 on the coupling side S2.In this embodiment, the opening portion 1-133 has a flange-like shapehaving an outer diameter which is formed larger than that of the barrelportion 1-131.

The can 1-130 is formed of non-conductive resin. The barrel portion1-131, the closing portion 1-132, and the opening portion 1-133 areformed integrally. A material of the can 1-130 is not limited to resin,and may also be ceramic or composite material of resin and ceramic. Inthis embodiment, the material of the can 1-130 is polyphenylene sulfide(PPS) resin. A thickness of each of the barrel portion 1-131 and theopening portion 1-133 can be set small, specifically, for example, in arange from 0.5 mm to 1.0 mm. A thickness of the closing portion 1-132 isset larger than that of the barrel portion 1-131, and can be set, forexample, in a range from 1.5 mm to 2.0 mm. It is preferred that thethickness of the barrel portion 1-131 be as small as possible in view ofthe improvement of motor characteristics. Moreover, it is preferred thata width of the opening portion 1-133 (having the flange-like shape) inthe direction of the rotation center axis line AR be as small aspossible in view of reduction in a length of an overhang correspondingto a distance between the bearing 1-51 and the end portion of the motor1-100 on the outer side S1.

The can 1-130 is mounted so that the stator core 1-111 and the barrelportion 1-131 are held in contact with each other in the circumferentialdirection. Further, the stator core 1-111 and the barrel portion 1-131are bonded with an adhesive at a position at which the stator core 1-111and the barrel portion 1-131 are held in contact. The stator core 1-111and the barrel portion 1-131 are bonded to each other with the adhesivein this manner. As a result, in this state, the stator core 1-111 andthe barrel portion 1-131 are integrated with each other. Therefore, amechanical strength of a part of the barrel portion 1-131 at a positioncorresponding to the stator core 1-111 can be reinforced by the statorcore 1-111. As a result, the thickness of the barrel portion 1-131described above can be reduced at the position corresponding to thestator core 1-111. As the adhesive, a silicone adhesive or an epoxyadhesive can be used in view of heat resistance during the operation ofthe vacuum pump 1-20.

The can 1-130 is mounted in a state in which an end surface of theprojecting portion 1-146 on the coupling side S2 and an end surface ofthe opening portion 1-133 on the outer side S1 are held in contact witheach other. At this time, an inner end surface of the projecting portion1-146 is held in contact with an outer surface of the barrel portion1-131 in the circumferential direction. The projecting portion 1-146 hasa function of positioning the can 1-130 in the direction of the rotationcenter axis line AR.

The reinforcing member 1-150 has an annular shape with an inner diameterapproximately equal to an outer diameter of the barrel portion 1-131.The reinforcing member 1-150 is fitted on the outer side (on thecoupling side S2) of the stator core 1-111 in the direction of therotation center axis line AR so that the reinforcing member 1-150 andthe barrel portion 1-131 are held in contact with each other in thecircumferential direction. An end portion of the reinforcing member1-150 on the outer side S1 is held in contact with the stator core1-111, whereas an end portion thereof on the coupling side S2 is fittedinto and held in contact with a cutout shape formed on the projectingportion 1-146 on the outer side S1. The reinforcing member 1-150 ispreferred to be a member made of resin or non-magnetic metal, which hasa tensile strength equal to or higher than 100 MPa.

Further, the reinforcing member 1-150 and the barrel portion 1-131 arebonded to each other with an adhesive at a position at which thereinforcing member 1-150 and the barrel portion 1-131 are held incontact with each other. The reinforcing member 1-150 and the barrelportion 1-131 are bonded to each other with the adhesive in this manner.As a result, in this state, the reinforcing member 1-150 and the barrelportion 1-131 are integrated with each other. Therefore, the mechanicalstrength of a part of the barrel portion 1-131 even on the coupling sideS2 of the stator core 1-111 can be reinforced by the reinforcing member1-150. As a result, a thickness of the part of the barrel portion 1-131on the coupling side S2 of the stator core 1-111 can be reduced. A partof the barrel portion 1-131, which is located on the coupling side S2 ofthe reinforcing member 1-150, is held in contact with the projectingportion 1-146. As a result, the mechanical strength of the part of thebarrel portion 131 is reinforced. It is apparent that the barrel portion1-131 and the projecting portion 1-146 may be bonded with an adhesive.

The reinforcing member 1-160 includes a first part 1-161, a second part1-162, and a third part 1-163. The first part 1-161 is a part of thereinforcing member 1-160, which is located at a position closest to thecoupling side S2, and has an annular shape with an inner diameterapproximately equal to an outer diameter of the barrel portion 1-131.The second part 1-162 has a flange-like shape extending coaxially fromthe first part 1-161 outward in the radial direction. The third part1-163 has an annular shape extending from an outer-side end portion ofthe second part 1-162 toward the outer side S1.

The reinforcing member 1-160 is fitted on the outer side of the statorcore 1-111 in the direction of the rotation center axis line AR so thatthe first part 1-161 and the barrel portion 1-131 are held in contactwith each other in the circumferential direction. At this time, an endportion of the first part 1-161 on the outer side S1 is located on theouter side S1 of the coil portion 1-113, and is located at the sameposition as that of an end portion of the barrel portion 1-131 of thecan 1-130 on the outer side S1 in the direction of the rotation centeraxis line AR. An end portion of the first part 1-161 on the couplingside S2 is held in contact with the stator core 1-111. Further, thefirst part 1-161 and the barrel portion 1-131 are bonded to each otherwith an adhesive at a position at which the first part 1-161 and thebarrel portion 1-131 are held in contact with each other. Therefore, amechanical strength of a part of the barrel portion 1-131 on the outerside S1 of the stator core 1-111 can be reinforced by the first part1-161. As a result, a thickness of the part of the barrel portion 1-131,which is located on the outer side S1 of the stator core 1-111, can bereduced.

A length of the second part 1-162 in a direction perpendicular to therotation center axis line AR is formed to be equal to a distance betweenthe outer surface of the barrel portion 1-131 and the inner surface ofthe frame main body 1-141. Thus, the third part 1-163 is held in contactwith the inner surface of the frame main body 1-141. By theconfiguration described above, the mechanical strength of the part ofthe barrel portion 1-131, which is located on the outer side S1 of thestator core 1-111, is further reinforced.

At a position on the frame main body 1-141, which corresponds to thethird part 1-163, a concave portion 1-147 is formed. An O-ring 1-154 isprovided in the concave portion 1-147. The O-ring 1-154 is compressed ina direction perpendicular to the rotation center axis line AR betweenthe frame main body 1-141 and the third part 1-163 so as to performsealing between the coupling side S2 and the outer side S1 of thereinforcing member 1-160.

Hermetically-sealed spaces are formed around the coil portions 1-112 and1-113 in a region between the frame main body 1-141 and the barrelportion 1-131. The coil portions 1-112 and 1-113 are housed in thehermetically-sealed spaces, respectively. Specifically, the coil portion1-112 on the coupling side S2 is housed in the space enclosed by theframe main body 1-141, the projecting portion 1-146, the reinforcingmember 1-150, and the stator core 1-111, whereas the coil portion 1-113on the outer side S1 is housed in the space enclosed by the frame mainbody 1-141, the first part 1-161, and the second part 1-162. Theenclosed space on the coupling side S2 is filled with a resin 1-171,whereas the enclosed space on the outer side S1 is filled with a resin1-172. With the configuration described above, the mechanical strengthof the barrel portion 1-131 at both end portions of the stator core1-111 can be further reinforced.

In the motor 1-100, it is preferred to set a linear expansioncoefficient of each of the reinforcing members 1-150 and 1-160 equal toor smaller than a linear expansion coefficient of the stator core 1-111.Similarly, it is preferred to set a linear expansion coefficient of eachof the resins 1-171 and 1-172 equal to or smaller than a linearexpansion coefficient of the stator core 1-111. By setting the linearexpansion coefficients as described above, a stress acting on the barrelportion 1-131 from the reinforcing members 1-150 and 1-160 and theresins 1-171 and 1-172 is reduced when compression heat is generated bydriving the vacuum pump 1-20 to thermally expand the reinforcing members1-150 and 1-160 and the resins 1-171 and 1-172. Therefore, themechanical strength required for the barrel portion 1-131 can bereduced. As a result, the thickness of the barrel portion 1-131 can bereduced. For the same reason, it is preferred to set a linear expansioncoefficient of the adhesive used to bond the stator core 1-111 and thebarrel portion 1-131 and to bond the reinforcing members 1-150 and 1-160and the barrel portion 1-131 equal to or smaller than the linearexpansion coefficient of the stator core 1-111. Similarly, it ispreferred to set the linear expansion coefficient of each of thereinforcing members 1-150 and 1-160 and the resins 1-171 and 1-172 equalto or smaller than a linear expansion coefficient of the frame main body1-141. However, the linear expansion coefficient of the frame main body1-141 is generally equal to or larger than that of the stator core1-111. Therefore, the linear expansion coefficient of each of thereinforcing members 1-150 and 1-160 and the resins 1-171 and 1-172generally becomes equal to or smaller than that of the frame main body1-141 as long as the linear expansion coefficient of each of thereinforcing members 1-150 and 1-160 and the resins 1-171 and 1-172 isset equal to or smaller than that of the stator core 1-111.

According to the motor 1-100 described above, the mechanical strength ofthe barrel portion 1-131 of the can 1-130 is reinforced by variousconfigurations described above. As a result, the thickness of the barrelportion 1-131 can be correspondingly reduced. Therefore, thecharacteristics of the motor 1-100 are improved. Moreover, by settingthe thickness of the closing portion 1-132 of the can 1-130 larger thanthat of the barrel portion 1-131, the mechanical strength required forthe closing portion 1-132 can be ensured.

The can 1-130 of the motor 1-100 can be suitably manufactured even byinjection molding. In the injection molding, in order to allow the resinto smoothly flow into a cavity of a mold, it is preferred that athickness of a molded product be uniform to some extent. Therefore, thecan 1-130 may be manufactured in the following manner. Specifically, thebarrel portion 1-131, the closing portion 1-132, and the opening portion1-133 are first formed by injection molding to have the same thicknessas that of the closing portion 1-132. Thereafter, the thickness of eachof the barrel portion 1-131 and the opening portion 1-133 is reduced bycutting work and the like. Moreover, in the injection molding, a slightgradient is provided to the molded product so that the molded product issmoothly demolded after the molding. As described above, when thethickness of each of the barrel portion 1-131 and the opening portion1-133 is reduced by cutting work and the like, the work can be conductedso as not to generate the gradient. In this manner, the barrel portion1-131 and the stator core 1-111, and the barrel portion 1-131 and thereinforcing members 1-150, 1-160 can be easily bonded with the adhesive.

1-B. Embodiment 1-B

FIGS. 3A and 3B illustrate a configuration of a can 1-230 of a vacuumpump according to Embodiment 1-B. A vacuum pump according to Embodiment1-B differs from that according to Embodiment 1-A only in a part of theconfiguration of the can, and the remaining points are the same as thoseof Embodiment 1-A. Therefore, for the can 1-230, only points differentfrom Embodiment 1-A are described below. FIG. 3A is a partial sectionalview of the can 1-230. FIG. 3B is a diagram of the can 1-230 as viewedfrom the coupling side S2.

Similarly to Embodiment 1-A, the can 1-230 includes a barrel portion1-231, a closing portion 1-232, and an opening portion 1-233. Theclosing portion 1-232 is slightly rounded at an end portion connected tothe barrel portion 1-231. On an inner surface of the closing portion1-232, ribs 1-234 are formed in a spaced manner in a circumferentialdirection. Each of the ribs 1-234 is formed to extend from an endportion of the barrel portion 1-231 on the outer side S1 toward thevicinity of a central portion of the closing portion 1-232. The ribs1-234 are formed so as to reach the vicinity of the central portion ofthe closing portion 1-232, while a thickness of the ribs 1-234 graduallydecreases from the end portion of the barrel portion 1-231 on the outerside S1. Therefore, the ribs 1-234 do not interfere with a mountingmember for the rotor 1-30 such as a bolt, which is provided in a spacein the vicinity of the rotation center axis line AR in a part of theinternal space located in the vicinity of the closing portion 1-232 ofthe can 1-230.

With the configuration described above, a strength of the closingportion 1-232 can be enhanced. Moreover, by the enhanced strength, athickness of the closing portion 1-232 can be correspondingly reduced.Therefore, as described above, when the molded product having thethickness equal to that of the closing portion 1-232 as an overallthickness is manufactured by the injection molding, and is thensubjected to the cutting work to manufacture the can 1-230, thethickness of the molded product obtained by the injection molding can bereduced. As a result, the amount of cutting work can be reduced.

Moreover, according to the configuration described above, the can 1-230has an inner diameter which decreases from the coupling side S2 to theouter side S1 on the cross section of the part of the can 1-230, onwhich the ribs 1-234 are formed. Correspondingly, specifically, by theamount of volume of the ribs 1-234, an internal spatial volume of thecan 1-230 is reduced. As a result, the amount of gas moving between theinterior of the can 1-230 and the vacuum pump 1-20 when the vacuum pump1-20 is driven is reduced. Specifically, the amount of gas passingthrough the bearing 1-51 provided between the internal space of the can1-230 and the internal space of the casing 1-40 of the vacuum pump 1-20is reduced. Therefore, the reduction in the amount of lubricant, whichis generated with the movement of gas, can be suppressed. As a result, aburden of maintenance and management of the vacuum pump 1-20 can bereduced.

Further, in the injection molding, the molded product is left in innermolds when the molded product is demolded after the molding. The can1-230 is provided with the ribs 1-234. Therefore, when the can 1-230 ismanufactured by the injection molding, the molded product is more likelyto be locked to the inner molds. As a result, the can 1-230 can beeasily manufactured.

1-C. Embodiment 1-C

FIG. 4 is a partial sectional view illustrating a configuration of a can1-330 of a vacuum pump according to Embodiment 1-C. As illustrated inFIG. 4, a closing portion 1-332 of the can 1-330 has a dome shape ofwhich a central portion expands from the coupling side S2 toward theouter side S1. A shape of an inner surface of the closing portion 1-332conforms to that of an outer surface thereof. With the can 1-330, amechanical strength of the closing portion 1-332 can be furtherimproved. Moreover, an inner diameter of the closing portion 1-332decreases from the coupling side S2 toward the outer side S1. Therefore,the same effects as those of Embodiment 1-B are obtained. It is apparentthat ribs may be formed on the can 1-330 as in the case of Embodiment1-B.

1-D. Embodiment 1-D

FIG. 5 is a sectional view illustrating a configuration in which a can1-430 and a stator core 1-411 of the vacuum pump according to Embodiment1-D are bonded. As illustrated in FIG. 5, in this embodiment, the can1-430 is bonded to the stator core 1-411 with an adhesive 1-481 throughan underlayer 1-482 formed on an outer surface of the can 1-430.Specifically, on the outer surface of the can 1-430, the underlayer1-482 is formed. The underlayer 1-482 is bonded to the stator core 1-411with the adhesive 1-481. In this embodiment, the underlayer 1-482 isformed only on a region of the outer surface of the can 1-430, to whichthe stator core 1-411 is bonded. However, the underlayer 1-482 may beformed over the entire outer surface of the can 1-430.

The underlayer 1-482 can be formed of any of various non-conductivematerials having a higher affinity for the adhesive 1-481 than the can1-430. As the non-conductive materials, for example, polyimide resin andcross-linking component may be used. The underlayer 1-482 may be formedby applying a paste material or may be formed by plating or coating.

With the configuration described above, even when the can 1-130 is madeof material having a relatively low affinity for the adhesive 1-481, forexample, engineering plastic such as PPS, a bonding strength between thestator core 1-411 and the can 1-430 is improved. Therefore, themechanical strength of the can 1-430 can be suitably reinforced by thestator core 1-411. As a result, a thickness of the can 1-430 can bereduced.

Further, the underlayer 1-482 may be formed of non-conductive materialhaving a larger tensile strength than the can 1-430. As such material,ceramic such as Al₂O₃ may be used. In this case, the underlayer 1-482may be formed by thermally spraying the ceramic onto the surface of thecan 1-430. With the configuration described above, the strength of thecan 1-430 having the reduced thickness can be reinforced.

In addition to or in place of the configuration of Embodiment 1-Ddescribed above, the can 1-430 may be bonded to the reinforcing members1-150 and 1-160 (see Embodiment 1-A) with the adhesive 1-481 through theunderlayer 1-482 although the illustration thereof is herein omitted.With the configuration described above, a bonding strength between thereinforcing members 1-150 and 1-160 and the can 1-430 is improved.Therefore, the mechanical strength of the can 1-430 can be furtherreinforced by the reinforcing members 1-150 and 1-160. Thus, thethickness of the can 1-430 can be further reduced.

1-E. Embodiment 1-E

FIG. 6 is a sectional view illustrating a configuration in which a can1-530 and a stator core 1-511 of a vacuum pump according to Embodiment1-E are bonded. FIG. 6 illustrates a cross section perpendicular to therotation center axis line AR. As illustrated in FIG. 6, the stator core1-511 includes a plurality of teeth 1-515 projecting toward the centerof the stator core 1-511. A coil 1-512 is wound around each of theplurality of teeth 1-515 in concentrated winding. Spaces 1-516 areformed on the inner circumferential side between end portions of theplurality of teeth 1-515. In each of the spaces 1-516, a non-conductivemember 1-585 to be engaged with the teeth 1-515 located on both sides ofthe non-conductive member 1-585 is provided.

The member 1-585 has a wedge-like shape. The members 1-585 are insertedinto the stator core 1-511 so as to close the spaces 1-516. In thisembodiment, the members 1-585 are made of glass epoxy resin. With theconfiguration described above, the can 1-530 and the teeth 1-515 of thestator core 1-511 are bonded with an adhesive 1-581. Further, in thespaces 1-516, the can 1-530 and the members 1-585 are bonded with theadhesive 1-581. The members 1-585 are engaged with the teeth 1-515.Therefore, the bonding between the can 1-530 and the members 1-585contributes to the improvement of the bonding strength between the can1-530 and the stator core 1-511. In this manner, a bonding area of theadhesive 1-581 is increased to enhance the bonding strength between thecan 1-530 and the stator core 1-511. A mechanical strength of the can1-530 can be further reinforced by the stator core 1-511. As a result, athickness of the can 1-530 can be further reduced.

The members 1-585 may be formed by filling the spaces 1-516 with aresin. Moreover, the resin used for filling may be an adhesive. In thiscase, it is preferred that the adhesive have a heat resistance to atemperature at which the motor 1-100 is used. Further, it is preferredthat a bonding strength of the adhesive be 1 kg/cm² (0.098 MPa) orhigher. The above-mentioned points are similarly applied to the adhesive1-581.

1-F: Variations 1-F-1. Variation 1-F-1

The shape of the closing portion of the can with the inner diameterdecreasing from the coupling side S2 toward the outer side S1, describedin Embodiments 1-B and 1-C, is not limited to the examples describedabove, and may be various. For example, the shape of the closing portionmay be conical, truncated conical, or convex. In such a case, ribs maybe formed on an outer surface of the closing portion. It is apparentthat ribs are formed on both the inner surface and the outer surface ofthe closing portion.

1-F-2. Variation 1-F-2

The shape of the barrel portion 1-131 of the can 1-130 is not limited tothe shape having an entirely reduced thickness. The thickness of thebarrel portion 1-131 may be only partially reduced. For example, only athickness of a portion of the barrel portion 1-131, which is held incontact with the stator core 1-111, may be reduced. The can having theshape described above may be manufactured by cutting work after theinjection molding.

2. Second Embodiment Group

According to one embodiment of the present invention, a canned motor tobe coupled to a vacuum pump and used as a rotary driving source for thevacuum pump is provided. The canned motor includes: a stator core; arotor provided on an inner side of the stator core; and a can made ofresin provided between the stator core and the rotor. The can isconfigured to separate the stator core and the rotor from each other.The can includes a barrel portion having a hollow shape and extending ina direction of a rotation center axis line of the rotor. At least one ofan outer-diameter side surface and an inner-diameter side surface of thebarrel portion is approximately horizontal with an inclination ofsmaller than 0.5 degrees with respect to the rotation center axis linewithin at least a part of a facing range which faces the stator core inthe direction of the rotation center axis line.

When the can made of resin is manufactured by injection molding, aslight gradient is formed on a molded product so that the molded productis smoothly demolded after molding. With the canned motor in theabove-mentioned embodiment, the gradient of the can is reduced.Therefore, the can and at least one of the stator core and the rotor canbe provided in a more parallel manner. Therefore, a distance between thestator and the rotor can be reduced. As a result, the motorcharacteristics can be improved.

According to one embodiment of the present invention, a thickness of thefacing range of the can may be smaller than a thickness of a remainingportion. According to the embodiment, the thickness of the facing rangeof the can is smaller than the thickness of the remaining portion.Therefore, the distance between the stator and the rotor can be furtherreduced. The mechanical strength of the can is reinforced by the statorcore in the facing range, whereas the mechanical strength is suitablyensured by its own thickness in the remaining portion. Therefore, themechanical strength of the entire can can also be ensured.

According to one embodiment of the present invention, a thickness of thecan on the inner diameter side may be larger on a first side of thefacing range in the direction of the rotation center axis line ascompared with a thickness of the facing range, whereas a thickness ofthe can on the outer diameter side may be larger on a second side of thefacing range, as compared with the thickness of the facing range. Thesecond side is opposite to the first side. According to the embodiment,the amount of processing is reduced to effectively process the moldedproduct when the can is manufactured as follows: the molded productincluding a portion corresponding to the barrel portion is initiallymanufactured by the injection molding; and then the thickness of aprocessed portion of the molded product is reduced by processing themolded product.

According to one embodiment of the present invention, a vacuum pump isprovided. The vacuum pump may include the canned motor in any one of theembodiments described above.

According to one embodiment of the present invention, there is provideda method of manufacturing a can for a canned motor, the can including ahollow barrel portion extending in a specific direction. The method ofmanufacturing the can includes: injection molding to manufacture amolded product including a portion corresponding to the barrel portion;and processing at least one of an outer-diameter side surface and aninner-diameter side surface of the molded product to reduce aninclination of the at least one of the outer-diameter side surface andthe inner-diameter side surface with respect to a specific direction andto manufacture the can. According to the embodiment, the can included inthe canned motor according to the embodiment described above can besuitably manufactured.

According to one embodiment of the present invention, the processing mayfurther include reducing the inclination of the at least one of theouter-diameter side surface and the inner-diameter side surface withrespect to the specific direction. Further, in the processing, theinner-diameter side surface of the molded product may be processed toreduce the thickness of the processed portion on the first side of themolded product. Moreover, the outer-diameter side surface of the moldedproduct may be processed to reduce the thickness of the processedportion on the second side of the molded product. In the embodimentdescribed above, the can having a larger thickness on the inner diameterside, as compared with the thickness of the facing range, on the firstside of the facing range in the direction of the rotation center axisline, and having a larger thickness on the outer diameter side, ascompared with the thickness of the facing range, on the second side ofthe facing range which is opposite to the first side can be suitablymanufactured.

According to one embodiment of the present invention, the injectionmolding described above is provided. Moreover, in place of theprocessing in the embodiment described above, there is providedprocessing at least one of the outer-diameter side surface and theinner-diameter side surface of the molded product to reduce thethickness of the processed portion of the molded product. In theembodiment described above, as compared with the case where the can ismanufactured only by the injection molding, the degree of freedom forthe shape of the can can be increased. Any combination of the variousembodiments described above is possible.

Further, according to one embodiment of the present invention, a cannedmotor is provided. The canned motor includes: a stator core; a rotorprovided on an inner side of the stator core; and a can made of resinprovided between the stator core and the rotor. The can is configured toseparate the stator core and the rotor from each other. The can includesa barrel portion having a hollow shape and extending in a direction of arotation center axis line of the rotor. At least one of anouter-diameter side surface and an inner-diameter side surface of thebarrel portion is approximately horizontal with an inclination ofsmaller than 0.5 degrees with respect to the rotation center axis linewithin at least a part of a range facing the stator core in thedirection of the rotation center axis line. The canned motor accordingto the embodiment described above can be applied to various types ofpumps. For example, the canned motor according to the embodimentdescribed above is applicable to liquid pumps and an air blower which isa kind of gas pumps in the broad sense of the term. Any combination ofthe canned motor according to this embodiment with the variousembodiments described above applicable to the vacuum pump is possible.In the following, a second embodiment group of the present invention isdescribed with the exemplification of more specific embodiments.Although the vacuum pump is described below as an example, embodimentsdescribed below are not limited to the vacuum pump as described above.

2-A. Embodiment 2-A

In Embodiment 2-A, an overall configuration of the vacuum pump 1-20 isthe same as that of Embodiment 1-A. Therefore, points different fromEmbodiment 1-A are mainly described below. FIG. 7 illustrates aschematic configuration of a motor 2-100 which rotationally drivesrotors 2-30. In the following description, a side of the motor 2-100 tobe coupled to a vacuum pump 2-20 (more specifically, the rotors 2-30) inthe direction of the rotation center axis line AR is also referred to asthe coupling side S2, whereas a side opposite to the coupling side S2 isalso referred to as the outer side S1. As illustrated in FIG. 7, themotor 2-100 includes a stator 2-110, a rotor 2-120, a can 2-130, and astator frame 2-140.

The stator frame 2-140 includes a frame main body 2-141 and a side plate2-142. The frame main body 2-141 has a cylindrical shape in which aninternal space is formed along the rotation center axis line AR. Theframe main body 2-141 includes a projecting portion 2-146. Theprojecting portion 2-146 is a portion which projects inward from aninner surface of the frame main body 2-141 and is formed in an annularshape around the rotation center axis line AR in the vicinity of an endportion of the frame main body 2-141 on the coupling side S2. A lengthof projection of the projecting portion 2-146 is formed so as to beapproximately equal to a length of projection of an opening portion2-133 from a barrel portion 2-131 (the details thereof are describedbelow). The side plate 2-142 has a circular plate shape, and closes anopening of the frame main body 2-141 on the outer side S1. A concaveportion 2-145 is formed on an end surface of the frame main body 2-141on the outer side S1. An O-ring 2-153 is provided in the concave portion2-145. The O-ring 2-153 is compressed in the direction of the rotationcenter axis line AR between the frame main body 2-141 and the side plate2-142 so as to perform sealing between the interior of the stator frame2-140 and the exterior thereof. The side plate 2-142 is mounted to theframe main body 2-141 with bolts (not shown). The stator frame 2-140 canbe formed of, for example, iron or aluminum. The stator 2-110, the rotor2-120, and the can 2-130 are housed in the internal space of the statorframe 2-140.

The stator 2-110 has a configuration in which coils are mounted to astator core 2-111. At both ends of the stator 2-110 in the direction ofthe rotation center axis line AR, coil portions 2-112 and 2-113 projectoutward from the stator core 2-111. By fitting the stator core 2-111into the interior of the frame main body 2-141 of the stator frame2-140, the stator 2-110 is fixed to the stator frame 2-140 coaxiallywith the rotation center axis line AR. The stator core 2-111 can beformed by, for example, laminating silicon steel plates. The rotor 2-120is provided coaxially with the rotation center axis line AR inside ofthe stator 2-110, and is directly coupled to a pump main shaft 2-34 ofthe rotor 2-30 of the vacuum pump 2-20.

The can 2-130 is provided between the stator 2-110 and the rotor 2-120described above. The can 2-130 separates the stator 2-110 and the rotor2-120 away from each other. The can 2-130 includes the barrel portion2-131, a closing portion 2-132, and the opening portion 2-133.

The barrel portion 2-131 has an approximately cylindrical shape, and isprovided coaxially with the rotation center axis line AR. The barrelportion 2-131 includes a first barrel portion 2-134 on the outer side S1and a second barrel portion 2-135 on the coupling side S2. The firstbarrel portion 2-134 is formed to extend over the entire range in whichthe stator core 2-111 is provided in the direction of the rotationcenter axis line AR and to face an inner surface of the stator core2-111. The range of the first barrel portion 2-131, which faces thestator core 2-111, is also referred to as a facing range FR.

The second barrel portion 2-135 is formed on the coupling side S2 of thefacing range FR. A thickness of the second barrel portion 2-135 islarger than that of the first barrel portion 2-134. Specifically, thesecond barrel portion 2-135 has a thickness which becomes larger towardthe outer diameter side as compared with the first barrel portion 2-134.More specifically, although an inner surface of the second barrelportion 2-135 is located at the same position as the first barrelportion 2-134 in the direction perpendicular to the rotation center axisline AR, an outer surface of the second barrel portion 2-135 is locatedon the outer side of an outer surface of the first barrel portion 2-134.As a result, an outer diameter of the second barrel portion 2-135 islarger than that of the first barrel portion 2-134. An end surface ofthe second barrel portion 2-135 on the outer side S1 is held in contactwith an end surface of the stator core 2-111 on the coupling side S2.

The closing portion 2-132 is an end surface of the can 2-130 on theouter side S1, and closes an internal space of the barrel portion 2-131at the end portion of the barrel portion 2-131 on the outer side S1. Inthis embodiment, the closing portion 2-132 has a shape with an outerdiameter and an inner diameter decreasing from the coupling side S2toward the outer side S1. A thickness of the closing portion 2-132 islarger than that of the first barrel portion 2-134. Specifically, theclosing portion 2-132 has a thickness which becomes larger toward theinner diameter side as compared with the first barrel portion 2-134.More specifically, although an outer surface of the closing portion2-132 is located at approximately the same position as the first barrelportion 2-134 in the direction perpendicular to the rotation center axisline AR in the vicinity of the first barrel portion 2-134, an innersurface of the closing portion 2-132 is located on the inner side of theinner surface of the first barrel portion 2-134.

The opening portion 2-133 is an end portion of the can 2-130 on thecoupling side S2, and forms an opening of the can 2-130 on the couplingside S2. In this embodiment, the opening portion 1-233 has a flange-likeshape having an outer diameter which is formed larger than that of thebarrel portion 2-131. An end surface of the opening portion 2-133 on theouter side S1 is held in contact with an end surface of the projectingportion 2-146 on the coupling side S2. The can 2-130 is positioned inthe direction of the rotation center axis line AR based on therelationship of contact between the end surface of the opening portion2-133 and the end surface of the projecting portion 2-146 and theabove-mentioned relationship of contact between the second barrelportion 2-135 and the stator core 2-111.

The can 2-130 is formed of resin. The barrel portion 2-131, the closingportion 2-132, and the opening portion 2-133 are formed integrally. Inthis embodiment, the material of the can 2-130 is polyphenylene sulfide(PPS) resin.

In the can 2130, a thickness of each of the closing portion 2-132 andthe second barrel portion 2-135 is set to have a mechanical strengthresistible to a pressure fluctuation generated during the operation ofthe vacuum pump 2-20. The thicknesses of the closing portion 2-132 andthe second barrel portion 2-135 are generally set based on a pressurevessel calculating method described in JIS B8267 and the like, and areabout 1.5 to 2.0 mm. In this embodiment, a thickness of the openingportion 2-133 (thickness in the direction of the rotation center axisline AR) is approximately the same as that of the second barrel portion2-135. In this manner, the resin can smoothly flow inside a cavity whenthe can 2-130 is manufactured by using the injection molding. Therefore,the manufacture is easy.

On the other hand, the first barrel portion 2-134 is formed to have asmaller thickness than that of each of the closing portion 2-132 and thesecond barrel portion 2-135. The thickness of the first barrel portion2-134 can be set, for example, in a range from 0.5 mm to 1.0 mm. Byreducing the thickness of the first barrel portion 2-134 in this manner,a distance between the stator core 2-111 and the rotor 2-120 is reduced.Therefore, motor characteristics of the motor 2-100 are improved.

An outer surface 2-134 a and an inner surface 2-134 b of the firstbarrel portion 2-134 are formed over the entire facing range FR so as tobe approximately horizontal with an inclination of 0.5 degrees orsmaller to the rotation center axis line AR. The can made of resin isgenerally manufactured by the injection molding. Moreover, in theinjection molding, a mold is provided with a slight gradient so as toenable smooth demolding after molding. The gradient is referred to as adraft angle, and is generally 1 to 2 degrees. As a result, the moldedproduct is formed with the gradient. As is apparent from the descriptiongiven above, the inclination generated due to the draft angle is reducedfor the outer surface 2-134 a and the inner surface 2-134 b of the firstbarrel portion 2-134. The shape of the barrel portion 2-131 describedabove is actualized by a method of manufacturing the can 2-130 describedlater.

It is preferred that the inclination be as small as possible. Forexample, the inclination is preferably set to be 0.3 degrees or smaller,more preferably 0.2 degrees or smaller, most preferably 0 degree. Inthis embodiment, the inclination of each of the outer surface 2-134 aand the inner surface 2-134 b is 0 degree. Specifically, the outersurface 2-134 a and the inner surface 2-134 b, and the rotation centeraxis line AR are precisely parallel to each other. In this embodiment,even the inclination of each of the outer surface and the inner surfaceof the second barrel portion 2-135 with respect to the rotation centeraxis line AR is 0 degree.

The can 2-130 is mounted so that the stator core 2-111 and the firstbarrel portion 2-134 are held in contact with each other in thecircumferential direction. The outer surface 2-134 a of the first barrelportion 2-134 does not have any inclination with respect to the rotationcenter axis line AR. Therefore, the stator core 2-111 and the firstbarrel portion 2-134 can be reliably brought into close contact witheach other over the entire facing range FR. In other words, a localclearance formed between the stator core 2-111 and the outer surface2-134 a due to the inclination is reduced corresponding to the reductionof the inclination of the outer surface 2-134 a with respect to therotation center axis line AR. Therefore, as compared with the case wherethe outer surface 2-134 a has the inclination with respect to therotation center axis line AR, a distance between the stator core 2-111and the rotor 2-120 can be reduced. Moreover, although the thickness ofthe first barrel portion 2-134 is reduced as compared with those of theclosing portion 2-132 and the second barrel portion 2-135 as describedabove, by the reliable close contact between the stator core 2-111 andthe first barrel portion 2-134 over the entire facing range FR, themechanical strength of the first barrel portion 2-134 is reinforced bythe stator core 2-111.

Moreover, the inner surface 2-134 b of the first barrel portion 2-134does not have any inclination with respect to the rotation center axisline AR. Therefore, the distance between the inner surface 2-134 b andthe rotor 2-120 becomes constant at any position in the direction of therotation center axis line AR. A specific distance is required to beensured between the inner surface 2-134 b and the rotor 2-120 in orderto avoid the interference therebetween. Therefore, when the innersurface 2-134 b has the inclination with respect to the rotation centeraxis line AR, a portion with a distance which is necessary minimum toavoid the interference is locally generated. On the other hand, with thefirst barrel portion 2-134, the distance between the stator core 2-111and the rotor 2-120 can be reduced by the amount of reduction in theinclination as compared with the case where the first barrel portion2-134 has the inclination with respect to the rotation center axis lineAR.

Further, in this embodiment, the stator core 2-111 and the first barrelportion 2-134 are bonded with an adhesive in a portion in which thestator core 2-111 and the first barrel portion 2-134 are held in contactwith each other. By bonding the stator core 2-111 and the first barrelportion 2-134 with the adhesive in this manner, the stator core 2-111and the first barrel portion 2-134 are integrated with each other inthis state. Therefore, the mechanical strength of the first barrelportion 2-134 can be further reinforced by the stator core 2-111. As theadhesive, a heat resistant adhesive such as a silicone adhesive or anepoxy adhesive can be used in view of heat resistance during theoperation of the vacuum pump 2-20.

The can 2-130 described above can be manufactured in the followingmanner. First, a molded product PM having portions corresponding to thebarrel portion 2-131, the closing portion 2-132, and the opening portion2-133 is manufactured by the injection molding. Next, an outer-diameterside surface and an inner-diameter side surface of the molded product PMare processed to reduce a thickness of the processed portions of themolded product PM to manufacture the can 2-130. With the manufacturingprocedure described above, the degree of freedom for the shape of thecan can be increased regardless of restrictions in shape resulting fromthe injection molding. The processing of the molded product PM isdescribed below in detail.

FIG. 8 illustrates a method of manufacturing the can, more specifically,a method of processing the molded product PM. FIG. 8 illustrates a crosssection of only a half of the molded product PM. In a portion of themolded product PM corresponding to the first barrel portion 2-134, anupper surface 2-211 and a lower surface 2-221 are formed. The uppersurface 2-211 and the lower surface 2-221 have the inclination of about1 to 2 degrees with respect to the rotation center axis line AR,resulting from the draft angle.

In this embodiment, both the upper surface 2-111 and the lower surface2-221 of the molded product PM are processed. An upper-surface sideportion 2-210 of the molded product PM on the upper surface 2-211 sideis subjected to cutting work to form the outer surface 2-134 a parallelto the rotation center axis line AR. In this embodiment, a cut portionis a portion on the outer side S1, that is, a portion corresponding tothe first barrel portion 2-134 and the closing portion 2-132. The cutportion only needs to include a portion corresponding to the firstbarrel portion 2-134, and cutting of the other portion can be omitted.

Similarly, a lower-surface side portion 2-220 of the molded product PMon the lower surface 2-211 side is subjected to cutting work to form theinner surface 2-134 b parallel to the rotation center axis line AR. Inthis embodiment, a cut portion is a portion on the coupling side S2,that is, a portion corresponding to the first barrel portion 2-134, thesecond barrel portion 2-135, and the opening portion 2-133. The cutportion only needs to include a portion corresponding to the firstbarrel portion 2-134, and cutting of the other portion can be omitted.

In this embodiment, the cutting work described above is performed bylathe machining. However, a technique of processing the molded productPM is not particularly limited, and any technique may be used as long asthe thickness of the desired portion of the molded product PM is reducedto form the desired shape. The processing technique may be, for example,grinding work, polishing work, etching, or a combination thereof.

With the manufacturing method described above, the can 2-130 describedabove can be suitably manufactured. For the upper surface 2-211 side ofthe molded product PM, only the outer side S1 is processed. For thelower surface 2-221 side, only the coupling side S2 is processed.Therefore, as compared with the case where the molded product PMentirely having a thickness larger than a required thickness is firstmanufactured and is then processed, the processing is effective withoutbeing needlessly long.

2-B: Variations 2-B-1. Variation 2-B-1

Only one of the outer surface 2-134 a and the inner surface 2-134 b ofthe first barrel portion 2-134 of the can 2-130 may have an inclinationequal to or smaller than 0.7 degrees with respect to the rotation centeraxis line AR. In this case, only one of the upper surface 2-211 side andthe lower surface 2-221 side of the molded product PM may be processed.Even in this manner, the effects described above are obtained to someextent as compared with the conventional configurations.

2-B-2. Variation 2-B-2

Only a part of the facing range FR of the first barrel portion 2-134 mayhave an inclination of 0.5 degrees or smaller with respect to therotation center axis line AR. Even in this manner, the effects describedabove are obtained to some extent as compared with the conventionalconfigurations.

2-B-3. Variation 2-B-3

The thickness of the facing range FR is not necessarily required to bereduced, and may be approximately equal to that of the closing portion2-132 or the second barrel portion 2-135. In this case, the moldedproduct PM may be subjected to minimum processing necessary for reducingthe inclination of the outer surface 2-134 a and the inner surface 2-134b of the first barrel portion 2-134 with respect to the rotation centeraxis line AR.

2-B-4. Variation 2-B-4

The can 2-130 is not necessarily required to have the shape closed onthe outer side S1. For example, the first barrel portion 2-134 may beformed to extend to the outer side S1 to be brought into contact withthe side plate 2-142 in a hermetically sealed manner. In this case, thethickness of the first barrel portion 2-134 on the outer side S1 of thefacing range FR may be larger than that of the facing range FR.

3. Third Embodiment Group

According to one embodiment of the present invention, there is provideda canned motor to be used to rotationally drive a vacuum pump, thecanned motor including a stator and a rotor separated from each other bya cylindrical resin partition covering an inter circumferential portionof the stator. An outer circumferential portion of the cylindrical resinpartition forms a meshing portion to be brought into meshing engagementwith magnetic-pole tooth portions of the stator in a radial direction.With the configuration described above, the outer circumferentialportion of the partition forms the meshing portion which is brought intomeshing engagement with the magnetic-pole tooth portions of the statorin the radial direction. With the configuration, a compressing forceacting inward in the radial direction on the partition during theoperation of the vacuum pump can be partially supported by the stator.Therefore, a thickness of the partition can be remarkably reduced ascompared with the conventional configurations. As a result, a gapbetween the stator and the rotor is remarkably reduced to improve motorefficiency.

According to one embodiment, the meshing portion has a complementarysectional shape to the magnetic-pole tooth portions so as to be held inclose contact with the magnetic-pole tooth portions. The meshing portionmay form ribs extending in a length direction of the partition. In theembodiment described above, the meshing portion has a complementarysectional shape to the magnetic-pole tooth portions so as to be held inclose contact with the magnetic-pole tooth portions, and the meshingportion forms the ribs extending in the length direction of thepartition. With the embodiment, the cylindrical partition can be easilyinserted into the stator so that the meshing portion is fitted to themagnetic-pole tooth portions. Therefore, the partition can be broughtinto close contact with the stator. As a result, the gap between thestator and the rotor can be remarkably reduced to improve the motorefficiency.

According to one embodiment of the present invention, the statorincludes slots formed between the magnetic-pole tooth portions. Themeshing portion may extend outward in the radial direction so as toretain windings in the slots. In the embodiment described above, themeshing portion extends outward in the radial direction so as to retainthe windings in the slots. Therefore, the use of winding retainingmembers (in other words, spacers), which are conventionally insertedinto the slots as independent members, can be omitted. Therefore, thenumber of components of the motor and the number of assembly steps canbe significantly reduced, and hence the manufacturing cost of the motorcan be significantly reduced.

According to one embodiment of the present invention, the meshingportion may include a concave portion which is open outward in theradial direction in the slot. According to this embodiment, the meshingportion includes the concave portion which is open outward in the radialdirection. Therefore, the radial meshing engagement with themagnetic-pole tooth portions with the meshing portion is maintained. Atthe same time, as compared with the conventional winding retainingmembers (in other words, the spacers), each having a flat strip-likeshape, the space inside the slot can be used to the maximum extent.Therefore, for example, the number of windings which can be housed inthe slot is increased to remarkably improve the motor efficiency.

According to one embodiment of the present invention, a vacuum pumpincluding the canned motor according to any one of the embodimentsdescribed above is provided.

According to one embodiment of the present invention, there is providedthe following canned motor. The rotor chamber is used under areduced-pressure atmosphere. Even when a large compressing force issubjected to the can member during the operation, the can member has nofear of deformation by the compressing force without increasing athickness of the can member.

According to one embodiment of the present invention, a magnetic gapbetween the stator and the rotor is minimized. As a result, a cannedmotor which is capable of remarkably improving the motor efficiency canbe provided.

According to one embodiment of the present invention, there can beprovided a canned motor which is capable of remarkably reducing thenumber of components and the number of assembly steps.

According to one embodiment of the present invention, there can beprovided a canned motor which allows the maximal use of the spacesinside the slots of the stator to remarkably improve the motorefficiency.

According to one embodiment of the present invention, there can beprovided a vacuum pump including the canned motor described above. Anycombination of the various embodiments described above is possible. Inthe following, a third embodiment group of the present invention isdescribed with the exemplification of more specific embodiments.

3-A. Embodiment 3-A

FIG. 9 is a perspective view illustrating the details of a configurationof a partition 3-18-1. The partition 3-18-1 is a component correspondingto the can 1-130 according to Embodiment 1-A. As a partition 3-18-2 (seeFIG. 11) has the same configuration as that of the partition 3-18-1,FIG. 9 illustrates only the partition 3-18-1. As illustrated in FIG. 9,the partition 3-18-1 has a substantially cylindrical barrel portion3-181. One end portion 3-182 of the barrel portion 3-181 in a lengthdirection is closed, whereas the other end portion 3-183 is open. Anannular flange portion 3-184 is formed on a circumferential edge of theopen end portion 3-183. The annular flange portion 3-184 is fixed to apump casing (corresponding to the casing 1-40 illustrated in FIG. 1)through bolts (not shown) in a hermetically sealed state. An outercircumferential surface of the barrel portion 3-181 includes ribsextending in the length direction of the partition 3-18-1. The ribs areformed by a meshing portion described below.

In the example illustrated in FIG. 9, the partition 3-18-1 is moldedintegrally into a cylindrical shape with a closed end. Specifically, theend portion 3-182 of the partition 3-18-1 on the side opposite to theannular flange portion 3-184 in the length direction is closed. However,the partition 3-18-1 may have an open end portion on the side oppositeto the annular flange portion 3-184. FIG. 10 illustrates an example of apartition 3-18-1′ including an opening end 3-182′ as described above. Inthis case, an independent closing member is fixed to the opening end3-182′ in a hermetically sealed state.

FIG. 11 is a sectional view of a motor portion M (corresponding to themotor 1-100 illustrated in FIG. 1) in the radial direction. FIG. 11illustrates a cross section perpendicular to a shaft of the motor M, andalso illustrates a cooling pipe and a mounting portion for the motor,which are not illustrated in the other embodiments. Permanent magnets3-19 are circumferentially provided to shafts 3-16′-1 and 3-16′-2 ofmotor rotors, which are directly coupled to a main shaft of a pump P. Astator 3-11 is provided on outer circumferences of the permanent magnets3-19 through the partitions 3-18-1 and 3-18-2. In this manner, the motorM is configured. The stator 3-11 includes a stator core 3-22, aplurality of magnetic-pole tooth portions 3-20 extending inward in theradial direction of the stator core 3-22, and windings 3-21 provided inslots 3-30 formed between the magnetic-pole tooth portions 3-20 so as tobe wound around the magnetic-pole tooth portions 3-20. A distal endportion of each of the magnetic-pole tooth portions 3-20 extendssubstantially in parallel to the permanent magnets 3-19 (in other words,in the circumferential direction) to form an extended portion (in otherwords, an expanded portion) 3-20-2 so as to increase a surface areaopposed to the permanent magnets 3-19. The extended portion 3-20-2 has alarger sectional area than that of a magnetic-pole base portion 3-20-1approximately linearly extending from the stator core 3-22 (see FIG.12).

The magnetic-pole tooth portions 3-20 constitute a brushless DC motor.In the brushless DC motor, motor rotors 3-16-1 and 3-16-2 rotate in theopposite directions in synchronization at positions symmetrical about acentral axis C between the motor rotors 3-16-1 and 3-16-2 so as to formthe opposite magnetic poles when the windings 3-21 are energized.Although a double-shaft brushless DC motor is used as the motor M inthis embodiment, a single-shaft brushless DC motor may be used in otherembodiments. Moreover, the motor to which this embodiment is applied isnot particularly limited as long as the motor is an electric motor.

This embodiment is suitably applied to the vacuum pump. In thisspecification, the term “vacuum pump” means a pump used in a state inwhich the pressure in the pump casing is reduced from the pressurearound the pump during the operation. Specifically, the term “vacuum”encompasses a relative vacuum, and does not only mean an absolutevacuum. Moreover, this embodiment may be applied to pumps other than thevacuum pump.

Next, referring to FIGS. 12 and 13, an embodiment of the partition3-18-1 is described in details. FIG. 12 is a partially enlarged view ofFIG. 11. In FIG. 12, the illustration of the windings 3-21 is omitted.FIG. 13 is a diagram illustrating the partition 3-18-1 alone, and is apartial sectional view across a length direction of the barrel portion3-181 of the partition 3-18-1.

Referring to FIG. 12, the distal end portion of each of themagnetic-pole tooth portions 3-20 of the stator 3-11 extendssubstantially in parallel to the permanent magnets 3-19 (in other words,in the circumferential direction) so as to increase a surface areaopposed to the permanent magnets 3-19, thereby forming the extendedportion 3-20-2 having a larger sectional area than that of each of themagnetic-pole base portions 3-20-1. Between the magnetic-pole toothportions 3-20, the slots 3-30 in which the windings 3-21 (not shown) arerespectively housed are formed. On the other hand, an outercircumferential portion of the partition 3-18-1 is configured so as toform the meshing portion which is radially brought into meshingengagement with the magnetic-pole tooth portions 3-20 in the respectiveslots 3-30. Specifically, projecting portions 3-185 which projectoutward in the radial direction of the partition 3-18-1 so as tocorrespond to the slots 3-30 are formed on the barrel portion 3-181 ofthe partition 3-18-1. As illustrated in FIG. 12, each of the projectingportions 3-185 has a complementary sectional shape to a distal endportion of corresponding one of the magnetic-pole tooth portions 3-20 sothat the outer circumferential portion of the partition 3-18-1 is fittedto the distal end portions of the magnetic-pole tooth portions 3-20 (inother words, the outer circumferential portion of the partition 3-18-1is held in close contact with the distal end portions of themagnetic-pole tooth portions 3-20). Specifically, as illustrated in thesectional view of FIG. 13, each of the projecting portions 3-185includes a base portion 3-185-1 and an extended portion (in other words,expanded portion) 3-185-2. The base portion 3-185-1 projects from thebarrel portion 3-181 in the radial direction, and has a small width (inother words, a size in the circumferential direction). The extendedportion 3-185-2 extends from a distal end of the base portion 3-185-1 inthe circumferential direction of the barrel portion 3-181, and has alarge width. The extended portion 3-185-2 includes meshing surfaces3-185-3 and a distal end surface 3-185-4. Each of the meshing surfaces3-185-3 is provided opposite to the extended portions 3-20-2 incorresponding one of the slots 3-30 in the radial direction so as tomesh with the extended portion 3-20-2 of the magnetic-pole tooth portion3-20 in the radial direction. The distal end surface 3-185-4 is flat,and is provided so as to be oriented to face the stator core 3-22.Grooves 3-186 into which the distal end portions of the magnetic-poletooth portions 3-20 can fit are formed by the projecting portions 3-185and parts of the outer surface of the barrel portion 3-181, which arelocated between the projecting portions 3-185. As described above, inthis embodiment, the meshing portion is formed by the projectingportions 3-185 of the partition 3-18-1 and the parts of the outersurface of the barrel portion 3-181, which are located between theprojecting portions 3-185.

When the pump P is rotationally driven by the canned motor M having theconfiguration described above, vacuum regions are formed in a pumpcasing 3-3 and rotor chambers 3-17-1 and 3-17-2. A large compressingforce F in the radial direction as illustrated in FIG. 12 acts on thepartition 3-18-1 defining the rotor chamber 3-17-1 and the partition3-18-2 defining the rotor chamber 3-17-2 by a differential pressurebetween an atmospheric pressure around the motor M and a pressure in thevacuum regions (in other words, a large tensile force toward theinterior of the rotor chambers 3-17-1 and 3-17-2 acts). In thisembodiment, however, the outer circumferences of the partitions 3-18-1and 3-18-2 form the meshing portions including the meshing surfaces3-185-3 which mesh with the magnetic-pole tooth portions 3-20 of thestator 3-11 in the radial direction. Therefore, a part of the radialcompressing force generated during the operation of the pump can besupported by the stator 3-11. Specifically, in the embodiment describedabove, a part of the compressing force is supported by the stator 3-11through the meshing surfaces 3-185-3. Therefore, it is not necessary tosupport all the compressing force by the partitions 3-18-1 and 3-18-2 asin the conventional cases. Therefore, even when the thickness of each ofthe partitions 3-18-1 and 3-182-2 is formed smaller than that in theconventional cases, there is no fear of inward buckling distortion ofthe partitions 3-18-1 and 3-18-2, which is caused by the compressingforce. Therefore, the thickness of the partitions 3-18-1 and 3-18-2located in the magnetic gaps can be significantly reduced as comparedwith the conventional thickness. As a result, the magnetic gaps can beminimized to improve the motor efficiency.

Moreover, as in the embodiment described above, it is preferred that thesectional shape of the meshing portion including the meshing surfaces3-185-3 be complementary to the distal end portions of the magnetic-poletooth portions 3-20. Moreover, as illustrated in FIGS. 9 and 10, it ispreferred that the meshing portion extend over the entire length of thepartitions 3-18-1 and 3-18-2 to form the ribs. In this manner, forassembly of the motor M, the partitions 3-18-1 and 3-18-2 can be easilyinserted into the stator 3-11 along the ribs so that the outercircumferential portions of the partitions 3-18-1 and 3-18-2 fit to thedistal end portions of the magnetic-pole tooth portions 3-20. In thismanner, the partitions 3-18-1 and 3-18-2 can be easily brought intoclose contact with the stator 3-11. Therefore, the gaps between thestator and the rotors can be minimized. In this regard, this embodimentcan be advantageously applied to any pumps other than the vacuum pump.In another embodiment, the ribs formed by the meshing portion are notrequired to continuously extend over the entire length of the partition3-18-1 (3-18-2) as illustrated in FIGS. 9 and 10. Alternatively, theribs may extend intermittently over a plurality of sections. Furtheralternatively, the ribs may extend over a part of the entire length ofthe partition 3-18-1 (3-18-2).

Further, in this embodiment, the meshing portion is formed to have aspecific radial size. As a result, the meshing portion can also functionas a winding retaining portion for retaining the windings in the slots3-30. An independent winding retaining member for retaining the windingin the slot of the stator, which is called “spacer”, is conventionallyused. The independent winding retaining member is generally a memberobtained by processing a resin material as a non-metallic material intoa strip. The winding retaining member is inserted into each of the slotsand used to retain the winding in the slot so as to prevent the windingfrom being unwound. The winding is fixed by filling the slot with aresin after the completion of the motor. The spacer is required toretain the winding until a resin filling step is finished. In anotherembodiment, for example, by setting a thickness of the extended portion3-185-2 of the projecting portion 3-185 of the embodiment describedabove to a specific thickness, the extended portion 3-185-2 may functionas the winding remaining portion in place of the conventional spacer.The extended portion 3-185-2 is a portion provided in each of the slots3-30, and therefore is not a portion located in the magnetic gap. Thus,even when the thickness of the extended portion 3-185-2 is increased,the motor efficiency is not affected thereby. With the configurationdescribed above, the independent winding retaining member is notrequired to be used. Therefore, the number of components and the numberof assembly steps of the canned motor can be significantly reduced.

In the embodiment described above, the projecting portion 3-185 isformed to have an approximately T-like sectional shape. Such a T-likesectional shape is provided because the distal end portion of each ofthe magnetic-pole tooth portions 3-20 of this embodiment is formed tohave an approximately inverted T-like shape. The sectional shape of eachof the projecting portions constituting the meshing portion can bechanged in accordance with the sectional shape of the distal end portionof each of the magnetic-pole portions 3-20 corresponding to theprojecting portions. An example of a projecting portion 3-185′ havinganother sectional shape is illustrated in FIG. 14. In this example, thedistal end portion of the magnetic-pole tooth portion 3-20 forms anextended portion 3-20-2′ having an approximately triangular sectionalshape. Therefore, the projecting portion 3-185′ includes anapproximately inverse triangular portion including meshing surfaces3-185′-3 and a distal end surface 3-185′-4. The meshing surfaces3-185′-3 mesh with oblique sides of the approximately triangular shapeof the extended portion 3-20-2′. The distal end surface 3-185′-4 isflat, and is provided so as to face the stator core 3-22. As in theembodiment described referring to FIGS. 12 and 13, a part of a force inthe compressing direction, which acts on the partitions 3-18-1 and3-18-2, can be supported by the stator 11 through the meshing surfaces3-185′-3. Further, the projecting portion 3-185′ includes a windingretaining portion 3-187 extending outward in the radial direction so asto be able to retain the winding (not shown) in corresponding one of theslots 3-30.

FIGS. 15 to 17 illustrate further examples of the sectional shape of themeshing portion. In the embodiments described above, each of the distalend surface 3-185-4 of the projecting portion 3-185 and the distal endsurface 3-185′-4 of the projecting portion 3-185′ forms a flat surface.However, in the examples illustrated in FIGS. 15 to 17, the meshingportion includes a concave portion (in other words, a groove) which isopen outward in the radial direction inside each of the slots 3-30. FIG.15 illustrates an example of a projecting portion 3-285 having arectangular groove 3-288 having a rectangular cross section formed on adistal end surface of a projecting portion having an approximatelyT-like cross section as illustrated in FIG. 13. Specifically, therectangular groove 3-288 having the rectangular cross section is formedin an approximately central portion of a distal end surface 3-285-4 ofthe projecting portion 3-285 in the width direction. As in theembodiment described above, an extended portion 3-285-2 extending from adistal end of a base portion 3-285-1 of the projecting portion 3-285 inthe width direction includes meshing surfaces 3-285-3 which are providedto face the extended portion 3-20-2 of the magnetic-pole tooth portion3-20 inside the slot 3-30. The meshing surfaces 3-285-3 mesh with theextended portion 3-20-2 in the radial direction. As a result, a part ofthe force in the compressing direction can be supported by the stator3-11. Further, in the example illustrated in FIG. 15, the rectangulargroove 3-288 is formed on the distal end surface 3-285-4. Therefore,even when the extended portion 3-285-2 is provided inside the slot 3-30,the space inside the slot 3-30 can be maximally used as the windingretaining space. Thus, the motor efficiency can be improved.

FIG. 16 illustrates an example of a projecting portion 3-385 including atriangular groove (in other words, a V-shaped groove) 3-388 having aninverted triangular cross section formed on a distal end surface of aprojecting portion of an approximately inverted triangular cross sectionas illustrated in FIG. 14. FIG. 17 illustrates an example of aprojecting portion 3-485 including an arc-like groove 3-488 having anarc-like cross section formed on a distal end surface of a projectingportion having an approximately T-like cross section as illustrated inFIG. 13. Even in the examples illustrated in FIGS. 16 and 17, similarlyto the example illustrated in FIG. 15, by forming the groove 3-388 onthe distal end surface of the projecting portion 3-385 or the groove3-488 on the distal end surface of the projecting portion 3-485, thespace inside the slot 3-30 can be maximally used as the windingretaining space while the meshing engagement of the meshing surfaces3-385-3 or 3-485-3 with the magnetic-pole tooth portions 3-20 in theradial direction is maintained. Therefore, the motor efficiency can beimproved. In the examples illustrated in FIGS. 16 and 17, the concaveportion 3-388 is formed on the distal end surface of the projectingportion 3-385 over the entire width direction, whereas the concaveportion 3-488 is formed on the distal end surface of the projectingportion 3-485 over the entire width direction. Similarly to the exampleillustrated in FIG. 15, however, the concave portion 3-388 or 3-488 maybe formed only on a part of the distal end surface.

This embodiment can be widely applied to the canned motors used for thepump, and can be suitably used for, in particular, the vacuum pumpincluding the rotor chamber used under the reduced pressure atmosphere.

4. Fourth Embodiment Group

According to one embodiment of the present invention, a canned motor tobe coupled to a vacuum pump and used as a rotary driving source for thevacuum pump is provided. The canned motor includes: a stator core; arotor provided on an inner side of the stator core; and a can providedbetween the stator core and the rotor. The can is configured to separatethe stator core and the rotor from each other. The can includes: abarrel portion having a hollow shape and extending in a direction of arotation center axis line of the rotor; and an opening portion forforming an opening of the barrel portion on a first side directlycoupled to the vacuum pump in the direction of the rotation center axisline. The stator core and the rotor are separated from each other in ahermetically sealed manner by the can and an O-ring provided on an outersurface of the opening portion of the can along a circumferentialdirection.

With the canned motor described above, the O-ring is provided on theouter surface of the can in the circumferential direction. Therefore, ascompared with the case where the O-ring is provided on the second-sideend surface of the can, a length of an overhang can be reduced by theamount of the space in which the O-ring is provided. In general, thevacuum pump is provided and assembled so that the direction of therotation center axis line becomes the horizontal direction (directionperpendicular to the vertical direction). Assuming such an arrangement,the O-ring is mounted on the surface in the horizontal direction in thisembodiment. Therefore, as compared with the case where the O-ring ismounted on the surface in the vertical direction, which is formed on thesecond-side end surface of the can, the O-ring is unlikely to be removedduring the assembly of the vacuum pump. Therefore, the assembly of thevacuum pump is facilitated.

According to one embodiment of the present invention, the can may beformed of resin. The opening portion may be formed to have a flangeshape, and a thickness of the flange shape in the directionperpendicular to the rotation center axis line may be larger than thatof the barrel portion. In the embodiment described above, even when thethickness of the barrel portion is set as small as possible to reducethe distance between the rotor and the stator so as to improve the motorcharacteristics, a sufficient stiffness of the opening portion can beobtained. Therefore, the O-ring can be suitably compressed to bedeformed to obtain good sealing performance.

According to one embodiment of the present invention, the can may beformed of resin. The opening portion may include a first part, a secondpart, and ribs. The first part is formed to extend from the barrelportion toward the outer side of the can in the direction crossing thedirection of the rotation center axis line. The second part is formed toextend from the first part toward the first side. The ribs are formedbetween the first part and the second part. A thickness of each of thefirst part and the second part may be equal to or larger than thethickness of the barrel portion and equal to twice the thickness of thebarrel portion or smaller. In the embodiment described above, even whenthe thickness of the barrel portion is reduced as much as possible toreduce the distance between the rotor and the stator, the openingportion is reinforced by the ribs to obtain a sufficient stiffness.Therefore, the O-ring can be suitably compressed to be deformed toobtain reliable sealing performance. In addition, the thickness of thecan falls within a predetermined range regardless of the part of thecan. Therefore, the can made of resin can be suitably manufactured bythe injection molding. Further, in the injection molding, a moldedproduct is left in inner molds when the molded product is demolded afterthe molding. In this embodiment, the molded product is more likely to belocked to the inner molds (male molds) by the ribs formed on the can. Asa result, the manufacture of the can made of resin by the injectionmolding is facilitated.

According to one embodiment of the present invention, a level-differenceportion formed by projecting the second side outward may be formed onthe outer surface of the barrel portion along the circumferentialdirection. The can may be mounted in a state in which thelevel-difference portion and the stator core are held in contact witheach other. In the embodiment described above, at the time of assemblyof the canned motor, the can can be positioned in the direction of therotation center axis line by the level-difference portion. Therefore, ascompared with the case where a projecting portion projecting toward theinner diameter side is formed on a part of the inner surface of thehollow stator frame into which the stator core is to be fitted, and theend portion of the can on the second side is formed to have aflange-like shape, and the projecting portion and the flange-like shapedend portion of the can come into contact with each other to position thecan in the direction of the rotation center axis line, the length of theoverhang can be reduced by a length of the projecting portion.

According to one embodiment of the present invention, the can mayinclude a closing portion for closing the internal space of the barrelportion on the second side opposite to the first side. In the embodimentdescribed above, the interior of the can can be easily closely sealed toseparate the stator core and the rotor from each other in a hermeticallysealed manner.

According to one embodiment of the present invention, a vacuum pump isprovided. The vacuum pump may include the canned motor in any one of theembodiments described above. Any combination of the various embodimentsdescribed above is possible.

Further, according to one embodiment of the present invention, a cannedmotor to be coupled to a pump and used as a rotary driving source forthe pump is provided. The canned motor includes: a stator core; a rotorprovided on an inner side of the stator core; and a can provided betweenthe stator core and the rotor. The can is configured to separate thestator core and the rotor from each other. The can includes: a barrelportion having a hollow shape and extending in a direction of a rotationcenter axis line of the rotor; and an opening portion for forming anopening of the barrel portion on a first side directly coupled to thepump in the direction of the rotation center axis line. The stator coreand the rotor are separated from each other in a hermetically sealedmanner by the can and an O-ring provided on an outer surface of theopening portion of the can along a circumferential direction. The cannedmotor according to the embodiment described above can be applied tovarious types of pumps. For example, the canned motor according to theembodiment described above is applicable to liquid pumps and an airblower which is a kind of gas pumps in the broad sense of the term. Anycombination of the canned motor according to this embodiment with thevarious embodiments described above applicable to the vacuum pump ispossible. In the following, a fourth embodiment group of the presentinvention is described with the exemplification of more specificembodiments. Although the vacuum pump is described below as an example,embodiments described below are not limited to the vacuum pump asdescribed above.

4-A. Embodiment 4-A

In Embodiment 4-A, an overall configuration of the vacuum pump 1-20 isthe same as that of Embodiment 1-A. Therefore, points different fromEmbodiment 1-A are mainly described below. FIG. 18 illustrates aschematic configuration of a motor 4-100 which rotationally drivesrotors 4-30. In the following description, a side of the motor 4-100 tobe coupled to a vacuum pump 4-20 (more specifically, the rotors 4-30) inthe direction of the rotation center axis line AR is also referred to asa coupling side S1, whereas a side opposite to the coupling side S1 isalso referred to as an outer side S2. As illustrated in FIG. 18, themotor 4-100 includes a stator 4-110, a rotor 4-120, a can 4-130, and astator frame 4-140.

The stator frame 4-140 includes a frame main body 4-141 and a side plate4-142. The frame main body 4-141 has a cylindrical shape in which aninternal space is formed along the rotation center axis line AR. Theside plate 4-142 has a circular plate shape, and closes an opening ofthe frame main body 4-141 on the outer side S2. The stator 4-110, therotor 4-120, and the can 4-130 are housed in the internal space of thestator frame 4-140.

The stator 4-110 has a configuration in which coils 4-112 are mounted toa stator core 4-111. By fitting the stator core 4-111 into the interiorof the frame main body 4-141 of the stator frame 4-140, the stator 4-110is fixed to the stator frame 4-140 coaxially with the rotation centeraxis line AR. The rotor 4-120 is provided coaxially with the rotationcenter axis line AR inside of the stator 4-110, and is directly coupledto a pump main shaft 4-34 of the rotor 4-30 of the vacuum pump 4-20.

The can 4-130 is provided between the stator 4-110 and the rotor 4-120described above. The can 4-130 separates the stator 4-110 and the rotor4-120 away from each other. The can 4-130 includes a barrel portion4-131, a closing portion 4-132, and an opening portion 4-133. The barrelportion 4-131 has an approximately cylindrical shape, and is providedcoaxially with the rotation center axis line AR. The barrel portion4-131 is formed so as to extend over the range in which the stator 4-110is provided in the direction of the rotation center axis line AR. On anouter surface of the barrel portion 4-131, a level-difference portion4-134 formed by projecting outward a part of the outer surface on thecoupling side S1 is formed along the circumferential direction. In thisembodiment, the level-difference portion 4-134 is formed continuously inan annular shape. Specifically, a thickness of the barrel portion 4-131becomes larger on the coupling side S1 of the level-difference portion4-143 than on the outer side S2 of the level-difference portion 4-134.In another embodiment, the level-difference portion 4-134 may beprojecting portions provided at spaced positions along thecircumferential direction.

The closing portion 4-132 is an end surface of the can 4-130 on theouter side S2, and closes an internal space of the barrel portion 4-131at the end portion of the barrel portion 4-131 on the outer side S2. Theopening portion 4-133 is an end portion of the can 4-130 on the couplingside S1, and forms an opening of the can 4-130 on the coupling side S1.In this embodiment, the opening portion 4-133 has a flange-like shapehaving an outer diameter which is formed larger than that of the barrelportion 4-131. Therefore, a thickness of the opening portion 4-133 inthe direction perpendicular to the rotation center axis line AR islarger than that of a part of the barrel portion 4-131 on the couplingside S1 of the level-difference portion 4-134, that of a part of thebarrel portion 4-131 on the outer side S2 of the level-differenceportion 4-134, and that of the closing portion 4-132.

In this embodiment, the can 4-130 is formed of resin. The barrel portion4-131, the closing portion 4-132, and the opening portion 4-133 areformed integrally. A thickness of the barrel portion 4-131 can be set,for example, in a range from 1.5 mm to 2.0 mm. A thickness of the barrelportion 4-131 can be set small, for example, in a range from 0.5 mm to1.0 mm. The can 4-130 is mounted so that the stator core 4-111 and apart of the barrel portion 4-131, which is located on the outer side S2of the level-difference portion 4-134, are held in contact with eachother in the circumferential direction. At this time, an end surface ofthe level-difference portion 4-134 is in a state in which the endsurface is held in contact with the stator core 4-111. Specifically, thelevel-difference portion 4-134 has a function as means for positioningthe can 4-130 in the direction of the rotation center axis line AR.

The motor 4-100 is mounted to the vacuum pump 4-20 by fixing the framemain body 4-141 of the stator frame 4-140 to a bearing member 4-50 withbolts (not shown). In FIG. 18, a cross section showing the mounting ofthe bolts is not illustrated. At this time, an end surface of theopening portion 4-133 of the can 4-130 on the coupling side S1 is heldin contact with an end surface of the bearing member 4-50 on the outerside S2. Moreover, the stator 4-110 and the rotor 4-120 are separatedfrom each other in a hermetically sealed manner by an O-ring 4-151provided on an outer surface of the opening portion 4-133 of the can4-130 in the circumferential direction. Specifically, a concave portion4-143 is formed on an inner surface of the frame main body 4-141 of thestator frame 4-140 along the circumferential direction. In the concaveportion 4-143, the O-ring 4-151 is provided. The O-ring 4-151 iscompressed in a direction crossing (in this case, perpendicular to) therotation center axis line AR between the opening portion 4-133 and theframe main body 4-141 so as to perform sealing between the stator 4-110and the rotor 4-120.

Further, on an end surface of the frame main body 4-141 on the couplingside 51, a concave portion 4-144 is formed. An O-ring 4-152 is providedin the concave portion 4-144. The O-ring 4-152 is compressed in thedirection of the rotation center axis line AR between the frame mainbody 4-141 and the bearing member 4-50 so as to perform sealing betweenthe rotor 4-120 and the outer side of the motor 4-100.

FIG. 19 illustrates a schematic configuration of a motor 4-100 a as acomparative example. In FIG. 19, each of components of the motor 4-100 ais denoted by a reference number with the letter “a” affixed to the endof the reference number denoting each of the components of the motor4-100 as the embodiment. For the motor 4-100 a, only points differentfrom the motor 4-100 are described below.

The stator frame 4-140 a includes a projecting portion 4-146 a. Theprojecting portion 4-146 a is a portion projecting inward from an innersurface of the frame main body 4-141 a. The projecting portion 4-146 ais formed in the vicinity of an end portion of the frame main body 4-141a on the coupling side 51. A length of projection of the projectingportion 4-146 a is formed approximately equal to a length of the openingportion 4-133 a. A width of the projecting portion 4-146 a in thedirection of the rotation center axis line AR is also referred to as awidth W1. A barrel portion 4-131 a of the can 4-130 a has approximatelythe same thickness at any positions in the direction of the rotationcenter axis line AR. Specifically, the level-difference portion 4-134provided to the motor 4-100 is not formed on the barrel portion 4-131 a.Thus, the can 4-130 a is positioned in the direction of the rotationcenter axis line AR by the contact of an end surface of the projectingportion 4-146 a on the coupling side 51 and an end surface of theopening portion 4-133 a on the outer side S2.

An annular concave portion 4-52 a is formed in the circumferentialdirection on an end surface of a bearing member 4-50 a on the outer sideS2. A width of the concave portion 4-52 a in the direction of therotation center axis line AR is also referred to as a width W2. In theconcave portion 4-52 a, an O-ring 4-151 a is provided. The O-ring 4-151a is compressed in the direction of the rotation center axis line ARbetween the opening portion 4-133 a and the concave portion 4-52 a toperform sealing between a stator 4-110 a and a rotor 4-120 a and betweenthe rotor 4-120 a and the exterior of the motor 4-100 a. The motor 4-100a is pressed against the bearing member 4-50 a in the direction of therotation center axis line AR so as to be mounted thereto. Therefore, asillustrated in FIG. 19, in general, the O-ring 4-151 a is provided so asto be compressed to be deformed in the direction of pressing, that is,in the direction of the rotation center axis line AR.

As is also apparent from the description given above, the projectingportion 4-146 a is provided so as to position the can 4-130 in thedirection of the rotation center axis line AR. Moreover, the projectingportion 4-146 a also has a role of assisting in stiffness of the openingportion 4-133 a when the opening portion 4-133 a is formed to have asmall thickness. Specifically, the projecting portion 4-146 a provides astiffness required to compress the O-ring 4-151 a in the direction ofthe rotation center axis line AR to the opening portion 4-133 a.

With the vacuum pump 4-20 described above, the O-ring 4-151 whichperforms sealing between the rotor 4-120 and the stator frame 4-140 isprovided on the outer surface of the can 4-130 (opening portion 4-133)along the circumferential direction. Therefore, as compared with thecase where the O-ring 4-151 a is provided on the end surface of the can4-130 (opening portion 4-133 a) on the coupling side 51 as in the caseof the motor 4-100 a, a length of an overhang of the vacuum pump 4-20can be reduced by the amount of a space in which the O-ring 4-151 isprovided, that is, the width W2.

In addition, the vacuum pump 4-20 can position the motor 4-100 in thedirection of the rotation center axis line AR by the level-differenceportion 4-134 at the time of assembly of the motor 4-100. Therefore, ascompared with the case where the projecting portion 4-146 a is formed onthe inner surface side of the stator frame 4-140 a and the openingportion 4-133 a of the can 4-130 a is formed to have a flange-like shapeso that the projecting portion 4-146 a and the opening portion 4-133 aare brought into contact with each other to position the can 4-130 a inthe direction of the rotation center axis line AR as in the case of themotor 4-100 a, the length of the overhang of the vacuum pump 4-20 can bereduced by the amount of a space for the projecting portion 4-146 a,that is, by the width W1.

Moreover, when the motor 4-100 is mounted to the vacuum pump 4-20 in astate in which the vacuum pump 4-20 is arranged horizontally, that is,the vacuum pump 4-20 is arranged so that the rotation center axis lineAR extends along the horizontal direction, the O-ring 4-151 is mountedon a surface in the horizontal direction. Therefore, as compared withthe case where the O-ring 4-151 a is mounted to a surface in thevertical direction as in the case of the motor 4-100 a, the O-ring 4-151of the vacuum pump 4-20 can be prevented from being removed from theconcave portion 4-143 to fall off in the middle of the assembly of thevacuum pump 4-20. As a result, the assembly of the vacuum pump 4-20 isfacilitated.

Moreover, in the vacuum pump 4-20, the can 4-130 is formed of resin. Thethickness of the opening portion 4-133 is larger than that of the barrelportion 4-131. Therefore, even when the distance between the rotor 4-120and the stator 4-110 is reduced by reducing the thickness of the barrelportion 4-131 as much as possible so as to improve the motor efficiency,a sufficient stiffness of the opening portion 4-133 can be obtained.Therefore, the O-ring 4-151 can be suitably compressed to be deformed toobtain good sealing performance.

4-B: Embodiment 4-B

FIGS. 20 and 21 illustrate a configuration of a can 4-230 of a vacuumpump according to Embodiment 4-B. The vacuum pump according toEmbodiment 4-B differs from that of Embodiment 4-A only in a part of theconfiguration of the can. The remaining points are the same as those ofEmbodiment 4-A. Therefore, for the can 4-230, only points different fromEmbodiment 4-A are described below. FIG. 20 is a partial sectional viewof the can 4-230, corresponding to FIG. 18. FIG. 21 is a view of the can4-230 as viewed from the coupling side 51.

Similarly to Embodiment 4-A, the can 4-230 includes a barrel portion4-231, a closing portion 4-232, and an opening portion 4-233. Athickness of the closing portion 4-232 is formed slightly larger thanthat of the barrel portion 4-231. The closing portion 4-232 has anarc-like shape expanding to the outer side S2. The opening portion 4-233includes a first part 4-234 and a second part 4-235. The first part4-234 is formed to extend from the barrel portion 4-231 toward the outerside of the can 4-230 in the direction crossing (in this case,perpendicular to) the direction of the rotation center axis line AR. Thesecond part 4-235 is formed to extend from the first part 4-234 to thecoupling side 51. A thickness of each of the first part 4-234 and thesecond part 4-235 falls in the range of 100% to 200% with respect to athickness of the barrel portion 4-231.

Ribs 4-236 are formed in the circumferential direction at spacedpositions between the first part 4-234 and the second part 4-235 asillustrated in FIGS. 20 and 21. Each of the ribs 4-236 is formed from aninner end portion of a top surface of the second part 4-235 on thecoupling side 51 to extend in the direction perpendicular to therotation center axis line AR toward the rotation center axis line AR byabout the same length as a length of the first part 4-234 in thedirection perpendicular to the rotation center axis line AR. Each of theribs 4-236 is also formed to have an inclination to form an acute anglewith respect to the rotation center axis line AR so as to reach a baseend portion of the first part 4-234 on the barrel portion 4-231 side. Inthe motor including the can 4-230 described above, the O-ring 4-151described above is provided on the outer surface of the second part4-235 of the opening portion 4-233.

With the can 4-230, the opening portion 4-233 is reinforced by the rib4-236 so that a sufficient stiffness is obtained even when the thicknessof the barrel portion 4-231 is reduced as small as possible. Therefore,the O-ring 4-151 can be suitably compressed to be deformed to obtainreliable sealing performance. In addition, the thickness of the can4-130 falls within a predetermined range regardless of the part of thecan 4-130. Therefore, the can 4-230 made of resin can be suitablymanufactured by the injection molding. Further, in the injectionmolding, the molded product is left in the inner molds when the moldedproduct is demolded after the molding. With the can 4-320, the ribs4-236 are formed on the can 4-320, and hence the molded product is morelikely to be locked to the inner molds. As a result, the manufacture ofthe can 4-230 made of resin by the injection molding is facilitated.

4-C. Variations 4-C-1. Variation 4-C-1

The opening portion 4-133 is not necessarily required to have theflange-like shape. For example, the opening portion 4-133 may be formedto have the same outer diameter as that of the barrel portion 4-131.Even in this case, the O-ring 4-151 may be provided between the openingportion 4-133 and the stator frame 4-140.

4-C-2. Variation 4-C-2

The O-ring 4-151 is not necessarily required to be provided between theframe main body 4-141 and the opening portion 4-133. For example, forsome shape of an interfacing surface of the bearing portion 4-50 withthe motor 4-100, the O-ring 4-151 may be provided between the bearingmember 4-50 and the opening portion 4-133 so as to be compressed to bedeformed in the direction perpendicular to the rotation center axis lineAR.

4-C-3. Variation 4-C-3

The concave portion 4-143 for providing the O-ring 4-151 therein is notnecessarily required to be formed on the frame main body 4-141. Forexample, a concave portion may be formed on the opening portion 4-133.

4-C-4. Variation 4-C-4

The material of the can 4-130 is not limited to resin, and variousmaterials can be used for the can 4-130. For example, the material ofthe can 4-130 may be non-magnetic metal such as stainless steel. Even inthis manner, the length of the overhang can be reduced as in Embodiments4-A and 4-B.

4-C-5. Variation 4-C-5

The can 4-130 is not necessarily required to have the shape closed onthe outer side S2. For example, the barrel portion 4-131 may be formedto further extend to the outer side S2 so as to be held in contact withthe side plate 4-142 in a hermetically sealed manner.

The embodiments of the present invention have been described above.However, the above-mentioned embodiments of the present invention aregiven to facilitate the understanding of the present invention, and donot mean to limit the present invention. The present invention can bechanged and modified without departing from the spirit thereof. Inaddition, it is apparent that equivalents are encompassed in the presentinvention. Moreover, the combination or the omission is possible foreach of the components described in the claims and the specificationwithin the range in which at least a part of the problems describedabove is solved or the range in which at least a part of the effectsdescribed above is obtained. For example, the configuration ofEmbodiment 1-C and that of Variation 1-F-1 can be actualized separatelyfrom the configurations of Embodiments 1-A and 1-B. For example, theconfiguration described above can be applied to a canned motor in whichthe stator core 1-111 and the barrel portion 1-131 are not bonded withthe adhesive or a canned motor without the reinforcing member 1-150.

What is claimed is:
 1. A canned motor to be coupled to a vacuum pump andused as a rotary driving source for the vacuum pump, the canned motorcomprising: a stator core; a rotor provided on an inner side of thestator core; and a can provided between the stator core and the rotor,the can being configured to separate the stator core and the rotor fromeach other, the can including a barrel portion having a hollow shape andextending in a direction of a rotation center axis line of the rotor,and an opening portion for forming an opening of the barrel portion on afirst side directly coupled to the vacuum pump in the direction of therotation center axis line, wherein the opening portion is formed to havea flange shape including: a first part formed to extend from the barrelportion toward the outer side of the can in the direction crossing thedirection of the rotation center axis line; and a second part formed toextend from the first part toward the first side, the opening portionincludes ribs formed in the circumferential direction of the can atspaced positions between the first part and the second part, the statorcore and the rotor are separated from each other in a hermeticallysealed manner by the can and an O-ring, the O-ring provided on an outersurface of the second part of the opening portion of the can along acircumferential direction and compressed in the direction crossing thedirection of the rotation center axis line, at least part of the ribsand the O-ring are provided on a line crossing the direction of therotation center axis line, and the can is formed of resin, and athickness of each of the first part and the second part is equal to orlarger than the thickness of the barrel portion, and equal to or smallerthan twice the thickness of the barrel portion.
 2. The canned motoraccording to claim 1, wherein a level-difference portion formed byprojecting the first side outward is formed on an outer surface of thebarrel portion along the circumferential direction, and the can ismounted in a state in which the level-difference portion and the statorcore are held in contact with each other.
 3. The canned motor accordingto claim 1, wherein the can includes a closing portion for closing theinternal space of the barrel portion on a second side opposite to thefirst side.
 4. A vacuum pump comprising: the canned motor in claim 1.